Ask The Vet: Cushing's Disease - February 07

In my previous responses, I do advocate using either test as a means of evaluating response to pergolide treatment. I do not think it is necessary to perform both tests for every assessment. More importantly, I think it is critical to be consistent, i.e. perform the same test at each re-evaluation of a Cushing’s (aka PPID, pituitary pars intermedia dysfunction) patient. Then, you and your veterinarian can compare “apples with apples.”

There is some concern about the use of steroids in horses with active laminitis or a history of laminitis. The belief is that steroids, including dexamethasone, may trigger a laminitis episode. While I will not discount any veterinarian’s personal experience, the fact is that very few documented reports exist. In fact, quoting a previous AAEP Convention presentation, “this risk appears low based on the results of two studies involving 17 horses and 52 horses, respectively, with PPID, in which none of the horses receiving dexamethasone developed signs of laminitis.” (1999 AAEP Proceedings, Messer, p. 145-147) From my own professional experience, I have not observed a worsening of laminitis following a low-dose dexamethasone suppression test. Again, some veterinarians have different experiences than mine. In those situations, the practitioner may suggest an alternate diagnostic test, such as the resting ACTH measurement. I think this is a reasonable alternative, but neither test has been shown to be much more “reliable” than the other. In summary, using a horse’s clinical signs in combination with diagnostic test results is the best way to diagnose PPID. Even then, none of our tests are perfect.

You are right in that many thyroid supplements for horses exist. That is simply a function of the competitive equine pharmaceutical market. All of the thyroid supplements should have detailed descriptions of their ingredients. This will allow you to compare products. In relation to your mare, I cannot tell you which product is “best.” In fact, I would debate whether long-term thyroid supplementation is even needed. On the topic of hypothyroidism in equine species, we know that true primary hypothyroidism in horses is quite uncommon. What is more likely occurring in your mare is a phenomenon in which another body illness, namely Cushing’s Syndrome, causes the thyroid hormones to be under-produced. While giving thyroid hormone supplementation may “normalize” the hormone measurement, it may not be needed indefinitely. In overweight horses with Cushing’s Syndrome, it can be a very useful aid in weight loss. If this applies to your situation, once a good body condition in your mare is achieved, you and your veterinarian could then consider stopping thyroid hormone supplementation.

Based on your “looks like a bear” comment, I would agree that Cushing’s Syndrome (aka pituitary pars intermedia dysfunction, PPID) is a very likely diagnosis for your mare.
Regarding treatment options, you have many. I recommend treating her because she could very well have other “silent” signs of the disease. I suggest watching her for excessive drinking/urination, on-and-off foot soreness and difficulty in clearing minor infections.

I can provide descriptions of traditional medication and management options. Pergolide is considered the most effective drug we have available for treatment of PPID. I must note that none of the medications discussed in this answer have been approved for use in the horse. When prescribed by your veterinarian, it is called an extra-label use of the drug. Several studies have compared the responses of horses treated with pergolide and those treated with another well-known option, cyproheptadine. Based on owner questionnaire responses, many owners felt their cyproheptadine-treated horses did better on the drug, versus when not receiving any medication. Many anecdotal reports exist of improvement in haircoat and other signs after treatment with this drug. However, one study refuted those conclusions. Those researchers found that after comparison of blood test responses following treatment of varying durations, more horses on pergolide had an improvement of blood test results for PPID than horses on cyproheptadine. In addition, in this study, a greater percentage of horses on pergolide showed improvement in their owners’ opinions as well. It is also reasonable for veterinarians to use a combination of pergolide and cyproheptadine to treat PPID, in those horses, which did not respond to treatment with one of the drugs alone. Another less popular treatment option is bromocriptine. It is uncommonly used, and I personally have no experience using it in PPID cases.

Herbal remedies are marketed as well, but very few controlled studies have been done on their effectiveness. One comparison study concluded that an herbal product containing chaste berry (Vitex agnus castus) had no beneficial effect on horses with PPID compared to a group treated with pergolide. It should be noted that standardization of herbal remedy contents is not required. Because of my lack of experience, I cannot provide you with advice on other natural treatment options. I will add though that very little information exists on the efficacy of natural treatments in PPID cases. I would suggest talking about regular health check-ups with your veterinarian (including dental and foot exams), and consider performing his/her recommended diagnostic tests for PPID. And yes, shaving her long hair will provide her much comfort throughout the year!

Unfortunately, the equine veterinary community has very little information on how a horse’s (or pony’s) body absorbs and metabolizes pergolide. The drug is not approved for use in equine species. Rather, it is used in an off-label manner to treat Cushing’s Syndrome (aka pituitary pars intermedia dysfunction, PPID). Thus, comments on pergolide’s effects are based on years of use of the drug in the “real” world. Therefore, I cannot comment on whether splitting a total daily dose in two portions is advantageous in any way. I do not have clients who have chosen that option. It is possible that your horse, Whiskey, became depressed after the initial dose of pergolide. However, it is thought that the drug may take several days to achieve systemic levels high enough to provide the desired effects. Also, I do not think this observed “sensitivity” necessarily suggests he does have PPID. If at all possible, I would recommend stopping therapy for 1-2 weeks, and then performing a plasma ACTH measurement. If this value is above the laboratory’s normal range for horses, then PPID would be much more likely. As for what dose of pergolide is needed, again I cannot provide a concise answer. I cannot interpret the volumes you offer without knowing the concentration of the pergolide liquid you use. Generally, most horses are started on a daily pergolide dose of 1 milligram per day (NOT the same as 1 cc). The attending veterinarian and owner can then assess a response to treatment after 4-6 weeks, with dose adjustments as needed. I emphasize that several weeks should be allowed at one dose before changes are made.

Regarding a performance career prognosis, you are correct in that predicting your horse’s path is very challenging. In my experience, depending on the severity of a horse’s signs and how manageable his signs are, then a performance career can be quite active and rewarding. My biggest concern with your horse would be his history of “sole soreness” and “intermittent unsoundness.” His Cushing’s syndrome diagnosis and the aforementioned signs would raise a flag for me about the possibility of chronic laminitis. While this hoof wall problem can be managed well, it is often the major reason for Cushing’s syndrome horse patients to leave an athletic life. I suggest talking with your veterinarian about this possibility.

I would agree with your understanding about pergolide therapy. In my opinion, it is a lifelong treatment and his dose may actually need to increase over time. My suggestion is to have repeat testing for Cushing’s syndrome anytime his signs seem to become worse or more obvious. This would include more frequent or severe foot lameness, worsening of the long, curly haircoat and increased drinking/urinating to name a few. With the help of your veterinarian, an increase in dose can be made and monitored closely. Your veterinarian can find a great review of patient management in the 2006 AAEP Convention Proceedings.

In terms of your gelding’s system becoming “reregulated,” in a true Cushing’s syndrome patient, I do not think this occurs. What your veterinarian MAY be referring to are those cases in which a horse does not have a clear-cut Cushing’s syndrome diagnosis, but may have outward signs that seem to be responsive to the drug. Again, I would refer you back to your veterinarian, as I am providing only an educated guess as to what he/she was explaining to you.

If treats are given infrequently and in small amounts, it is not necessary to “ban” them from the diet. By this I mean, feeding of one carrot or apple as a treat after a good ride or lesson, or as a tool in behavior modification. If you speak of a horse or pony who is being offered treats often throughout the day, it depends on that animal’s sensitivity to the treat and its glycemic index. Bottom line is that most treats don’t provide that much sugar. To be cautious, homemade horse treats can be made as well. I apologize for not providing a recipe, but they are available.

The questions you pose are common ones and unfortunately difficult to answer. That is because each Cushing’s Syndrome patient’s response to springtime grass is different. While some animals can graze for several hours a day with no negative consequences, other horses and ponies diagnosed with this syndrome may eat for less than an hour and develop mild laminitis signs subsequently. For your pony, I would ask if he has a history of laminitis following access to fresh grass? If he does, I would strongly encourage continuous use of the muzzle. If he does not, I would first suggest making a turnout plan with the help of you veterinarian. I would start by allowing him access to spring grass with the muzzle on at all times. After a few days, you might try 20-30 minutes of grazing without the muzzle, and then monitor him closely for any signs of a laminitis flare-up. How to proceed depends on the pony’s response.

I would also suggest gathering information on the type of grass he will be eating. You may find help from your area’s agricultural extension service, if possible. Some grasses have higher non-structural carbohydrate (NSC) content than others, and I would avoid exposing your pony to grass in that high NSC category. In fact, because the risk of recurrent laminitis is high with your pony, I would suggest using the muzzle as long as there is edible grass available. He will learn to accept the few sprigs of grass coming through the muzzle. In summary, your goals as this pony’s owner are providing a safe and clean environment, low NSC feedstuffs, regular foot and dental care and daily pergolide treatment.

You and your veterinarian have made some great management changes for your gelding, particularly the lower NSC diet. Visible improvements in a recently diagnosed Cushing’s Syndrome (aka pituitary pars intermedia dysfunction, PPID) patient are often very gradual. It is important to be a patient observer. Although a tight timeline cannot be given to you, I would expect that your gelding’s coat length and quality and his patchy sweating will improve within 2-4 months. The symptoms you listed may not be fully resolved in this time frame, but you should notice changes for the better. To monitor him, I would suggest continuing as you are – ensuring that he is not overfed, planning for regular farrier visits and continuing to exercise him regularly. I would also suggest getting a body weight tape. Your veterinarian can show you how to use this simple tool. This tape provides an estimate of a horse’s weight, and I think it is imperative to helping maintain a PPID patient’s body condition. Your veterinarian’s clinic can teach you about horse body condition scoring; we recommend that any horse or pony’s body condition score be kept between 5 and 6 (scale is 1-9). In addition, I would suggest that you plan for repeat blood testing for PPID with your veterinarian. This follow-up testing, along with a veterinary evaluation of your horse’s condition, attitude, foot/hoof health and dental health, will help to determine if the pergolide dose is appropriate. Anytime a pergolide dose change is made, I would again recommend repeat testing 1-2 months after the dose change is made. As for your gelding’s “weepy” eye, I am challenged to identify a specific cause for the excess tearing or discharge. Some animals do this for long periods with no negative consequences. Some eye discharge can be caused by inflammation or infection to a variety of eye structures. I’m sure your veterinarian can help to rule many of those possibilities in or out. Lastly, if you and your veterinarian are still concerned, an exam by a veterinary ophthalmologist who works with horses may be considered.

A single sample test for thyroid hormone levels is not the diagnostic test of choice for hypothyroidism in horses. The preferred test is called the TRH Stimulation test and this requires multiple blood samples to be collected. Also, it is often difficult to perform because the TRH needed for the test can be very difficult to find. It is not a commercially available “test kit.” Thus, unfortunately, assessing a horse’s thyroid gland responsiveness is a challenge in today’s world.

On the topic of hypothyroidism in equine species, we do know that true primary hypothyroidism in horses is quite uncommon. What is more likely occurring in your gelding is a phenomenon in which another body illness causes the thyroid hormones to be under-produced. A possible explanation is that your gelding does have Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID). While giving thyroid hormone supplementation may “normalize” the hormone measurement, it may not be addressing the underlying problem. Thus, I would suggest talking with your veterinarian about performing PPID testing. I would recommend the dexamethasone suppression test or a resting ACTH test. Both of these methods are well described in the 2006 AAEP Convention Proceedings. In addition, these proceedings describe evaluation of horses and ponies for equine metabolic syndrome and insulin resistance. Please refer to other Veterinary Rounds answers for more detail on these topics. If your veterinarian does not have access to this, he/she may contact your area’s veterinary teaching hospital or referral practices for guidance. A teaching hospital may also provide advice on performing a TRH Stimulation test.

It is most likely that your mare’s condition is deteriorating due to the lack of medical treatment for her Cushing’s Syndrome. While pergolide is expensive, even in generic form, it is considered the most effective drug we have available for treatment of Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID). I must note that none of the medications discussed in this answer have been approved for use in the horse. When prescribed by your veterinarian, it is called an extra-label use of the drug. Several studies have compared the responses of horses treated with pergolide and those treated with another well-known option, cyproheptadine. Cyproheptadine is cheaper, but not by a huge margin, in my opinion. Based on owner questionnaire responses, many owners felt their cyproheptadine-treated horses did better on the drug. Many anecdotal reports exist of improvement in haircoat and other signs after treatment with this drug. However, another controlled study refuted those conclusions. It is also reasonable for veterinarians to use a combination of pergolide and cyproheptadine to treat PPID, in those horses which did not respond to treatment with one of the drugs alone. Another less popular treatment option is bromocriptine. It is uncommonly used, and I personally have no experience using it in PPID cases. Other herbal remedies are marketed as well, but very few controlled studies have been done on their effectiveness. One comparison study concluded that an herbal product containing chaste berry (Vitex agnus castus) had no beneficial effect on horses with PPID compared to a group treated with pergolide. It should be noted that standardization of herbal remedy contents is not required.

Also, if you are able to start pergolide treatment again, I would encourage you to be patient when waiting for improvements after treatment is started. It can take several weeks, if not a few months, for obvious visible signs to become apparent to you as the owner. I would also suggest having her body clipped during the high heat and humidity times of the year. This can make her much more comfortable. Food options are a financial consideration too. Beet pulp – without molasses – and fat sources like corn oil can be added to help your mare regain some body weight. I would also suggest using a weight tape to regularly check her body weight, i.e. every 1-2 weeks. It is also good to give her a body condition score at each of these weight measurements. Information on body condition scoring in horses can be found on this site in the Health Articles section under the Body Condition category, as well as from your veterinarian’s office.

I agree that Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID), and/or insulin resistance (IR) should be considered as explanations for your gelding’s signs. In fact, he does have a clinical sign of PPID – namely his recurrent laminitis episodes. He may also be showing signs of a more recently recognized collection of signs called “equine metabolic syndrome (EMS).” The proper terminology is highly debated because we still know so little about this disorder. In EMS, it is thought that fat stores (aka adipose tissue) overproduce the hormone cortisol; the pituitary gland functions normally. Signs in this syndrome are (1) a history of laminitis or suspected past episodes, (2) abnormal fat accumulations in the crest of the neck, at the tail head, and (3) insulin resistance (IR). IR is a problem that horses from both groups – PPID patients and EMS patients – can have. Please refer to earlier Veterinary Rounds answers for more detailed information about IR.

I am curious what type of testing for PPID has been done in the past. The more reliable tests to perform are the dexamethasone suppression test and the resting plasma ACTH measurement, as you mentioned. In fact, these tests can be done on a horse already being treated with pergolide. Typically, one or both of these tests are done before pergolide is prescribed; then repeat tests are done after 1-2 months of treatment. In this way, response to pergolide therapy can be followed through visible changes as well as through improved test results. It must be emphasized that none of these tests are 100 percent sensitive and specific for diagnosis of PPID. In horses with more advanced PPID, the common sign of the long, curly haircoat can be as good as a blood test in making the diagnosis. The bigger challenge now is making a PPID diagnosis at a much earlier stage in the disease process. That is a current, primary focus of many equine endocrine disease researchers.

For Equine Metabolic Syndrome (EMS), testing options are still debated as the equine medical community learns more about this syndrome. One important factor is to test for PPID, in order to rule out that syndrome as a cause of the patient’s signs. In addition, in order to evaluate a horse or pony for insulin resistance (IR), it is recommended to measure the horse’s resting insulin concentration as well as perform an insulin-glucose sensitivity test. This test requires several blood samples to be collected over a relatively short period of time. It can be done in the field, but is often not practical for the busy, ambulatory veterinarian. Some also suggest calculating a horse’s glucose:insulin ratio following a meal. Your veterinarian can find further testing descriptions for EMS, PPID and IR in the 2006 AAEP Convention Proceedings. I strongly encourage your veterinarian to use this resource. If your gelding is doing well currently while on pergolide treatment, I would take this as a positive response to the therapy and support of a diagnosis of PPID. If your need for more or better answers to your questions continues, yes you could stop treatment for at least 4 weeks, and then perform PPID, EMS and IR testing. I strongly suggest you discuss these options with your veterinarian and other advisors first.

I can offer some suggestions to you, and also highly recommend that your veterinarian review the recent 2006 AAEP Convention Proceedings, which include an excellent section on equine endocrinology. First, I will refer to Cushing’s Syndrome in equine species as pituitary pars intermedia dysfunction (PPID). I must emphasize that an individual horse’s PPID test results can vary considerably over time. Many horses and ponies fit an “inconclusive” category while showing some of Cushing’s Syndrome’s classical signs. The bottom line is that the equine veterinary community does not have any one, perfect test for PPID. That said, it is often suggested to repeat such blood tests in horses suspected of having PPID. With your gelding’s signs of long haircoat, obesity and severe laminitis, he very well may be a case of PPID. It is possible that at some times, his hormone levels are abnormal, and at other times, they are normal. He may also be showing signs of a more recently recognized collection of signs called “equine metabolic syndrome (EMS).” The proper terminology is highly debated because we still know so little about this disorder. In this disorder, it is thought that fat stores (aka adipose tissue) overproduce the hormone cortisol; the pituitary gland functions normally. Signs in this syndrome are (1) a history of laminitis or suspected past episodes, (2) abnormal fat accumulations in the crest of the neck, at the tail head, and (3) insulin resistance (IR). IR is a problem that horses and ponies from both groups – PPID patients and EMS patients – can have.

At this point, because accurate diagnosis can be so challenging, I think it is reasonable to treat with pergolide and see if your gelding improves. The drug itself has never been studied carefully in horses, in terms of how it is absorbed, metabolized, etc. Thus, I do not find your statement that “(pergolide) may progress whatever disorder he has brewing” is accurate. Knowing the cost of this therapy, I can also understand the financial strain. If you choose to discontinue pergolide treatment, paying close attention to his non-structural carbohydrate (NSC) content in his diet will still be very important. Most experts suggest an NSC content below 12 percent. I would suggest monitoring him for signs of PPID, including chronic infections, repeated bouts of laminitis, excessive water drinking and urination. If some or all of these signs begin to show, then consider PPID testing and pergolide treatment at that time. For any horse with PPID or EMS, it is always important to provide regular health check-ups, including dental and farrier care, regular exercise as well as an appropriate diet.

I recommend that your veterinarian examine her left eye as soon as possible. Conditions affecting the eye are not commonly reported as symptoms of Cushing’s Syndrome. A more likely scenario is that your mare injured her eye during her seizure-like episode. Other possible explanations exist, but it is most critical to have the eye examined, so a diagnosis and treatment plan can be made by your veterinarian. The gray/bluish color and excess tearing are not normal, and are likely signs of eye inflammation or infection.

The answers to your nutrition questions depend on the area in which you live and the conditions in which the hay is grown. Hay does not necessarily need to be “rich” in order to provide a good source of nutrients. Based on your description, your gelding is likely not getting many calories on a daily basis from the Top Choice Lite®. In order to provide detailed advice on what nutrients he may need more of, you really need to have the hay analyzed. This forage analysis will provide information on the protein, carbohydrate, vitamin and mineral content. I would encourage this and subsequent diet planning with the aid of your veterinarian. There are also veterinary nutritionists available at veterinary teaching hospitals or in private practice. As always, I recommend feeding forage and concentrates with low non-structural carbohydrate content (less than 12 percent is advised by many experts).

If these options are not possible, I would suggest weighing your hay flakes, in order to know how many pounds of forage he is being fed each day. Typically, an adult horse on a maintenance diet needs 1.5 - 2 pounds of dry matter feed intake each day for every 100 pounds of body weight. Thus, a healthy, “backyard” 1000-pound horse needs 15-20 pounds of dry matter intake a day. To correct for hay that is lost to scatter and dropping, this equates to about 22-25 pounds of hay each day. This is only a guideline for feeding your horse. I would also suggest having a salt block available free choice. Again, more detailed advice about supplementation cannot be given until hay analysis has been done on your local hay. I suggest talking with your veterinarian about feed analysis options, and then formulation of a good diet for your insulin-resistant gelding. In addition, performing tests to rule in or rule out Cushing’s Syndrome would also be warranted, as well as re-evaluation of his insulin and glucose responses to his feed. It is possible that he is a Cushing’s Syndrome patient with associated insulin resistance. Your veterinarian can find good reviews of these topics in the 2006 AAEP Convention Proceedings.

First, let me clarify some terminology. Cushing’s Syndrome in horses and ponies is also called pituitary pars intermedia dysfunction (PPID). In fact, this is the preferred term used in equine veterinary medicine. “Pre-Cushing’s” is a term put into the mix because so little is known about early manifestations and progression of PPID. Many horses and ponies are called “highly suspicious” because not all signs and results point to a diagnosis of PPID. An example would be a horse with chronic, low grade laminitis and increased water intake, but with a normal response to a dexamethasone suppression test. I find the phrase “highly suspicious” more appropriate than “pre-Cushing’s.” If you are still curious about PPID as a diagnosis, I would suggest talking to your veterinarian about repeat testing for PPID. It may seem redundant, but diagnosis of PPID in its earlier stages is one of the biggest challenges equine veterinarians face. Also, some studies have shown that dexamethasone suppression test results can very considerably over time, even in horses with many, classic signs of PPID. There are also some documented seasonal variations in ACTH, a hormone that often has abnormally high concentrations in PPID. Thus, repeat testing of suspect PPID patients is often indicated.

Determining the proper dose of pergolide for a horse or pony is challenging. Oftentimes, an initial low dose is prescribed with the intent to monitor the patient’s symptoms and blood test results after several weeks of treatment. In addition, one of the more common side effects of pergolide can be a poor appetite. When this occurs, it is suggested that the initial dose be stopped for a few days. Then pergolide is started at half of the initially prescribed daily dose. Most horses will return to eating normally. This dose should be continued for about 1 month, followed by repeat PPID testing. If test results show an improvement, the dose can remain the same. I will also add that an animal’s dose changes over time, so an increase may be necessary down the road. Also, pergolide’s dose range is quite large. Thus, two horses of the same body weight may respond very well to two different pergolide doses. For review, I refer your veterinarian to the 2006 AAEP Convention Proceedings for thorough examples regarding PPID diagnosis and management.

Diarrhea, meaning increased water content of feces and increased frequency of defecation, is not a commonly reported symptom of Cushing’s Syndrome. It is possible that other management changes you made in his diet and other daily routines played a role in the end of his chronic gastrointestinal problem.

Based on your description of this Dutch Thoroughbred cross mare, I agree that Cushing’s Syndrome (aka pituitary pars intermedia dysfunction – PPID) would not be an obvious diagnosis. However, in patients earlier in the syndrome’s progress, horses and ponies can present with very mild symptoms, ranging from minor coat changes to intermittent, undetermined foot lameness. It sounds as though your feeding regimen for her has been very effective in promoting and maintaining good coat and body condition. Keep that going! If you and/or the owner are still curious about PPID as a diagnosis, I would suggest talking to the attending veterinarian about repeat testing for PPID. It may seem unnecessary, but diagnosis of PPID in its earlier stages is one of the biggest challenges equine veterinarians face. I also suggest that this mare’s veterinarian review the 2006 AAEP Convention Proceedings on endocrinology (if he/she has not done so already). Lastly, it is true that low fertility rates are a reported clinical problem in mares with PPID. With proper management and treatment (if a positive PPID diagnosis is made), many mares can be managed through pregnancy successfully. If this mare has signs and PPID test results that are difficult to interpret, a “definitive” diagnosis may not be achievable. However, continue your current diet plan because maintaining a healthy body condition throughout pregnancy and lactation is always critical.

You have been through a very frightening episode with your mare. You pose good questions, and they are somewhat difficult for me to answer without having seen the test results, which have been performed. Regarding your diet questions, if your mare does in fact have Cushing’s Syndrome, or pituitary pars intermedia dysfunction (PPID), keeping her on a low glycemic index, low non-structural carbohydrate (NSC) diet is ideal. Although insulin resistance (IR) is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods, which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise. An important recommendation is to feed grass hay or other feed sources, which are low in non-structural carbohydrates (NSC). Although more scientific research is needed, it is believed that NSC can negatively affect IR-susceptible horses by (1) providing excessive sugar intake and thus worsen IR, as occurs in diabetic people, and (2) large amounts of NSC may change the large intestine’s bacterial flora; this is thought to lead to greater production of laminitis “trigger-factors.” These theories are the reason why discussion of low-NSC feedstuffs is so common. Forage analysis of your hay is strongly encouraged to accurately determine the NSC content of your hay. The Buckeye Nutrition feed is a decent choice for a concentrate. I am unsure if this feed, in particular, has been evaluated for its effects on a horse’s blood sugar and insulin responses following a meal. Nonetheless, it seems to be a fair choice. As for feeding alfalfa hay, it has long been considered a “rich” feed. However, the nutrient content, i.e. crude protein, NSC, fructans, can all vary depending on the climate conditions and soil environment under which it grows. Ideally, I would again suggest having your pure alfalfa forage analyzed for nutrient content. If the NSC content is more than 12 percent, or the crude protein content is approaching 20 percent or more, this alfalfa hay would not be appropriate for your mare. Alfalfa hay with more stemmy components and lower NSC and protein can be well tolerated by PPID patients. If testing of forage is not an option, you may attempt a trial and error period of adding a small amount of your legume hay to her diet, and then assess how she does. It must be stressed that she may not tolerate alfalfa well, and it could lead to the negative effects mentioned above. I also suggest discussing these options with your veterinarian.

Regarding her nervous system signs, PPID can be associated with signs such as seizures, ataxia (decreased awareness of where feet and limbs are placed) and blindness. To my knowledge, reports have not been published, which describe induction of PPID in a horse following systemic steroid treatment. In a horse unaffected by PPID, and then given a large dose of injectable steroid, I would expect the administered steroid would cause the animals’ own internal production of cortisol to decline. This is based on the biochemical process called negative feedback. How the administration of steroids affected the test results for your mare is challenging and depends on the timing of the two events. If questions still exist about the steroid medication’s effects, I would suggest repeating the blood test to diagnose PPID. I suggest using the dexamethasone suppression test or the plasma ACTH measurement. If she does have PPID, I would also encourage you to reconsider use of pergolide, especially when her signs of the disorder become more obvious. For your veterinarian’s reference, testing methods and long-term management of PPID cases are well described in the 2006 AAEP Convention Proceedings.

For Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID), there are a variety of diagnostic tests available. The options fall into two categories: dynamic tests, which assess responsiveness of the horse’s endocrine glands, and single sample tests, which serve as “screening” tools for PPID.

Dynamic test options include the dexamethasone suppression test (DST), the diurnal cortisol rhythm, the thryotropin releasing hormone (TRH) stimulation test, and a combined DST/TRH stimulation test. Of these, the DST is probably the most widely accepted. In this test, a patient’s cortisol level is measured first, then a test dose of exogenous (from an outside source) steroid is given. A second cortisol measurement is taken 15-19 hours after this test steroid dose. A diagnosis is made when the second cortisol measurement fails to go below a set cortisol concentration. Some limitations of this test are that it requires multiple veterinary visits, and that the test dose of steroid may worsen a horse’s laminitis (if present). It should be noted that occurrence of this latter concern is not well documented.

Single sample test options include resting plasma ACTH (adrenocorticotropic hormone) concentration, serum insulin concentration and other pituitary gland products. ACTH is one of many hormones overproduced by the dysfunctional pituitary gland in patients with PPID. It also is the primary hormone responsible for stimulating greater cortisol production by the adrenal gland. One caveat is that ACTH can be elevated outside this normal range during certain months, namely in early fall. It is theorized to be due to seasonal effects on normal pituitary hormone production. What this means is that a normal horse may have an elevated ACTH during this time of the year, and be wrongly diagnosed with PPID. Also, after collection of blood from a horse, the sample requires special handling. If possible for an owner, it is often a smart choice to have both the DST and ACTH measurement performed on your horse or pony.

Lastly, it must be emphasized that none of these tests are 100 percent sensitive and specific for diagnosis of PPID. In horses with more advanced PPID, the common sign of the long, curly haircoat can be as good as a blood test in making the diagnosis. The bigger challenge now is making a PPID diagnosis at a much earlier stage in the disease process. That is a current, primary focus of many equine endocrine disease researchers.

For Equine Metabolic Syndrome (EMS), testing options are still debated as the equine medical community learns more about this syndrome. One important factor is to test for PPID, in order to rule out that syndrome as a cause of the patient’s signs. In addition, in order to evaluate a horse or pony for insulin resistance (IR), it is recommended to measure the horse’s resting insulin concentration as well as perform an insulin-glucose sensitivity test. This test requires several blood samples to be collected over a relatively short period of time. It can be done in the field, but is often not practical for the busy, ambulatory veterinarian. Your veterinarian can find further testing descriptions for EMS, PPID and IR in the 2006 AAEP Convention Proceedings. I strongly encourage your veterinarian to use this resource.

The signs of Cushing’s Syndrome, or pituitary pars intermedia dysfunction (PPID), involve many body systems. The list includes:

1) Failure to shed fully
2) Long, sometimes curly, haircoat – this can begin as long hairs along the jaw line and “feathers” near the fetlocks
3) Increased water intake and urination, called polyuria/polydipsia (PU/PD)
4) Chronic infections
5) Repeated laminitis episodes, sometimes with associated hoof abscesses
6) Excess, or inappropriate, sweating
7) Loss of muscle mass (later in process, if horse is untreated) – typically noticed over the back and hind quarters, as well as the “pot-bellied” appearance

In my professional experience, horses that have PPID and are left undiagnosed and untreated can still live for many years. However, their outward signs will continue to become more obvious, including an ever-lengthening haircoat, excess sweating, laminitis, chronic infections, and LOTS of water drinking and urinating. Many of these problems can be dealt with by an owner, however, the risks of infections that won’t heal and repeated bouts of laminitis are not chances I would want to take. I am not able to provide you with a life expectancy for a horse with untreated PPID, but I am confident that it is shorter than a horse which receives treatment and regular geriatric health check-ups. Again, this is all hypothetical, since no testing has been performed on your gelding. I would suggest talking about regular health check-ups with your veterinarian, and consider trying to save the funds needed to run the recommended diagnostic tests. In the end, your horse may or may not have PPID, but at least you will have that knowledge as he ages.

The signs of Cushing’s Syndrome, or pituitary pars intermedia dysfunction (PPID), involve many body systems. The list includes:

1) Failure to shed fully
2) Long, sometimes curly, haircoat – this can begin as long hairs along the jaw line and “feathers” near the fetlocks
3) Increased water intake and urination, called polyuria/polydipsia (PU/PD)
4) Chronic infections
5) Recurrent episodes of laminitis
6) Excess, or inappropriate, sweating
7) Loss of muscle mass (later in process, if horse is untreated) – typically noticed over the back and hind quarters, as well as the “pot-bellied” appearance

The terms Cushing’s and insulin resistance (IR) are often used together. I’ll aim to provide some clarification and explain how these two medical terms are related. Pituitary pars intermedia dysfunction is a disorder of a portion of the equine pituitary gland. To be brief, a variety of pituitary hormones are over-produced; one of these is ACTH, the hormone responsible for stimulation of cortisol production and release from the adrenal glands. Horses and ponies with PPID may exhibit a variety of the signs listed above. Although IR is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. The possible mechanisms behind IR are numerous and can be discussed with your veterinarian. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. In summary, IR can occur in a horse with PPID, or other equine metabolic disorders, but does not always appear to be present in PPID patients. I recommend to your veterinarian that he/she refer to the 2006 AAEP Convention Proceedings for an excellent review of these topics.

Your horse’s localized heat, sweating and hair color change is a rare finding and I am sure a bit frustrating for you. Although excess sweating is a common outward sign observed in horses and ponies with Cushing’s Syndrome, it is typically NOT localized, as with your horse. I agree with your veterinarian that your horse’s abnormality is most likely due to focal damage to a structure called the sympathetic trunk. This bunch of nerve fibers includes those involved with the sympathetic nervous system, including those which control sweat glands. When injured, this often leads to inappropriate sweating.

Identification of the root cause can be very difficult, and successfully curing the problem is highly unlikely. The good news is that horses can be maintained very well with this disorder. Systemic steroid treatment is worth a try, as your veterinarian suggested, but again it is unlikely that this change will return to normal function. The use of alternative medicine options, such as acupuncture, is an option for you. Since I am not trained in nor certified to perform acupuncture, I am not a good person to answer your questions about its application with your horse. I suggest locating a certified veterinary acupuncturist in your area. Your veterinarian, your state’s veterinary medical association or a veterinary teaching hospital in your area may be able to help you locate someone.

Based on the subtle signs you describe in your mare, I agree that Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID), and/or insulin resistance (IR) should be considered as explanations for your mare’s signs. If she has PPID, it is expected that, if left untreated and as she ages, her haircoat will get longer and curlier, and shedding will become delayed. The excess fat near her tail head and around her eyes (that’s the puffiness) are also common manifestations of PPID in horses. She may also be showing signs of a recently recognized collection of signs called “equine metabolic syndrome (EMS).” The proper terminology is highly debated because we still know so little about this disorder. In this disorder, it is thought that fat stores (aka adipose tissue) overproduce the hormone cortisol; the pituitary gland functions normally. Signs in this syndrome are (1) a history of laminitis or suspected past episodes, (2) abnormal fat accumulations in the crest of the neck, at the tail head and (3) insulin resistance (IR). A problem that horses from both groups – PPID patients and EMS patients – can have is insulin resistance.

Although IR is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. The possible mechanisms behind IR are numerous and can be discussed with your veterinarian. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise. An important recommendation is to feed grass hay or other feed sources, which are low in non-structural carbohydrates (NSC). NSC content below 12 percent is suggested for IR horses and ponies. Also, if more calories are needed, fat sources, such as vegetable oil or rice bran, are excellent choices instead of grains and feeds with high molasses content. Higher fiber content in the daily diet is also encouraged. This can be found in beet pulp and many commercially produced pelleted feeds.

In your situation, limiting grazing time is a good idea. I would also recommend having diagnostic testing done for PPID, EMS, and possibly IR. Depending on the test results, a daily regimen of pergolide treatment may be prescribed, in addition to recommendations for her diet, exercise, hoof and dental care as she ages. The body fat and puffy eye complaints may improve over time, with good management, but no one can promise you a complete elimination of these complaints. It is also critical that she have regular hoof care provided. I would suggest that your program’s veterinarian take x-rays of all four feet, to assess for evidence of past laminitis (founder). Your veterinarian can find some very informative PPID, EMS and IR information in the 2006 AAEP Annual Convention Proceedings.

You ask some very good questions about the vast world of equine endocrinology. One thing to consider is that an individual horse’s Cushing’s Syndrome test results can vary considerably over time. Many horses and ponies fit this “inconclusive” category while showing some of Cushing’s Syndrome’s classical signs. The bottom line is that the equine veterinary community does not have any one, perfect test for PPID. That said, it is often suggested to repeat such blood tests in horses suspected of having PPID. With your gelding’s signs of lack of shedding and a thicker neck crest, he very well may be an early case of PPID. It is possible that at some times, his hormone levels are abnormal, and at other times, they are normal. He may also be showing signs of a more recently recognized collection of signs called “equine metabolic syndrome (EMS).” The proper terminology is highly debated because we still know so little about this disorder. In this disorder, it is thought that fat stores (aka adipose tissue) overproduce the hormone cortisol; the pituitary gland functions normally. Thus, in my opinion, the term of “pre-Cushing’s” is not appropriate. Signs in this syndrome are (1) a history of laminitis or suspected past episodes, (2) abnormal fat accumulations in the crest of the neck, at the tail head and (3) insulin resistance (IR). IR is a problem that horses from both groups – PPID patients and EMS patients – can have.

Although IR is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. The possible mechanisms behind IR are numerous and can be discussed with your veterinarian. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods, which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise. An important recommendation is to feed grass hay or other feed sources, which are low in non-structural carbohydrates (NSC). Forage analysis of your hay is strongly encouraged to accurately determine the NSC content of your hay. NSC content below 12 percent is suggested for IR horses and ponies. Also, if more calories are needed, fat sources, such as vegetable oil or rice bran, are excellent choices instead of grains and feeds with high molasses content. Higher fiber content in the daily diet is also encouraged. This can be found in beet pulp and many commercially produced pelleted feeds.

In your situation, it is expected that any horse treated with Thyro-L will lose weight and likely have more energy. This is because Thyro-L provides extra thyroid hormone, the hormone which determines the animal’s metabolic rate. Thus, the more thyroid hormone, the higher the metabolic rate, meaning weight loss and a higher activity level, etc. Thyro-L can be quite useful to aid in weight loss in an overweight horse. However, because true, primary hypothyroidism is so rare in horses, I would suggest consideration of using Thyro-L only as a short-term therapy to achieve weight loss goals with your horse. Fortunately, chronic laminitis has not been a problem for your gelding. However, with his possible PPID, EMS or IR diagnosis, limiting NSC intake is likely a good idea for him, as it may help maintain good insulin sensitivity, regardless of his underlying disease. It is important too that his diet contains adequate vitamin and mineral content. In my opinion, these efforts will be more beneficial to your gelding’s health than chaste berry supplements. Anecdotal reports exist that chaste berry is helpful to PPID horses. However, a comparison study concluded that an herbal product containing chaste berry (Vitex agnus castus) had no beneficial effect on horses with PPID compared to a group treated with pergolide (the most common medication for PPID in horses). It should be noted that standardization of herbal remedy contents is not required. At this time, we do not know enough about all of these endocrine disorders to be able to recommend preventative measures. I recommend discussing IR further with your veterinarian, including testing for IR (resting insulin and/or combined glucose-insulin test) and repeat testing for PPID. He/she can find some very informative PPID, EMS and IR information in the 2006 AAEP Annual Convention proceedings. Also, with any PPID patient, regular health check-ups are critical to long-term care. This includes basic blood work, dental care and regular foot/hoof trimming and care.

I am assuming that the medication recommended by your veterinarian is pergolide (brand name, Permax®). While pergolide is expensive, even in generic form, it is considered the most effective drug we have available for treatment of Cushing’s Syndrome, aka pituitary pars intermedia dysfunction (PPID). I must note that none of the medications discussed in this answer have been approved for use in the horse. When prescribed by your veterinarian, it is called an extra-label use of the drug. Several studies have compared the responses of horses treated with pergolide and those treated with another well-known option, cyproheptadine. Based on owner questionnaire responses, many owners felt their cyproheptadine-treated horses did better on the drug. Many anecdotal reports exist of improvement in haircoat and other signs after treatment with this drug. However, one study refuted those conclusions. The researchers found that after comparison of blood test responses following treatment of varying durations, more horses on pergolide had an improvement of blood test results for PPID than horses on cyproheptadine. In addition, in this study, a greater percentage of horses showed improvement in their owners’ opinions as well. It is also reasonable for veterinarians to use a combination of pergolide and cyproheptadine to treat PPID, in those horses, which did not respond to treatment with one of the drugs alone. Another less popular treatment option is bromocriptine. It is uncommonly used, and I personally have no experience using it in PPID cases. Other herbal remedies are marketed as well, but very few controlled studies have been done on their effectiveness. One comparison study concluded that an herbal product containing chaste berry (Vitex agnus castus) had no beneficial effect on horses with PPID compared to a group treated with pergolide. It should be noted that standardization of herbal remedy contents is not required. Lastly, another drug option is available overseas. It is called trilostane, but is not readily available to U.S. veterinarians. Also, less is known about its effectiveness in horses with PPID, and it is even more expensive than pergolide. In conclusion, before making a decision about whether to invest this money in pergolide treatment, I would suggest talking with your veterinarian about testing the two, suspect PPID-affected horses. I also suggest that your veterinarian review the 2006 AAEP Convention Proceedings, which includes good examples of PPID case management.

Without examining your gelding myself, I cannot make a suggestion on other possible causes for his eye problem. It is true that horses with Cushing’s Syndrome often have difficulty in clearing infections from their body, even with appropriate therapy. Is your horse receiving daily medication for Cushing’s Syndrome, like pergolide? If not, his untreated endocrine disease MAY be playing a role in his persistent eye problem. Also, I would strongly recommend that you and your veterinarian consider a referral to an equine ophthalmologist. An ophthalmologist will have experience in diagnosing and treating more challenging and rare eye diseases, which can be very difficult to identify and treat in the field setting.

Regarding your 8-month old filly, I strongly recommend that laboratory work of her blood and urine be performed by your veterinarian. To my knowledge, a diagnosis of Cushing’s Syndrome, or pituitary pars intermedia dysfunction (PPID), has not been made in a horse as young as your filly. It may be possible, but highly unlikely. Again, I suggest talking with your veterinarian about performing a variety of tests, including a complete blood count, a FULL serum chemistry profile (includes BUN, creatinine, albumin, globulins, electrolytes), a urinalysis and urine specific gravity and possibly diagnostic tests for PPID. The tests I typically use are the overnight dexamethasone suppression test or the plasma ACTH test. Your veterinarian can find further testing information in the 2006 AAEP Convention Proceedings. As for her diet, I would be careful of feeding too much grain. My basic suggestions would be to provide a majority of her calories from hay and grazing, and provide added calories through your grain mixes. PER DAY, I would suggest feeding no more than 0.5 to 1.25 lbs. of grain for every 100 lbs. of her body weight. This is in addition to her hay and grazing. Using a body weight tape would be a great way for you to monitor her body condition. She may in fact need slightly more protein content than what you feed now, i.e. in the range of 12-15 percent crude protein content. Again, before making any diet changes, please discuss the blood testing options and possible diet changes with your veterinarian. The signs she is showing – increased water intake, long hair coat pattern, localized hair loss or dry skin – are rare findings in a weanling. Her test results may provide some answers, or at least point your veterinarian in the right direction to finding some answers for you.

Your current management of your horse sounds reasonable, but it is challenging for me to be more specific without being more familiar with your horse’s symptoms, as your veterinarian is. Over time, your feeding, exercise, foot care and dental care methods will change, as your horse’s signs change. I do not have experience using Triple Crown Lite™, but it seems to be a decent choice for a suspect Cushing’s Syndrome (aka pituitary pars intermedia dysfunction, PPID) patient. Also, avoiding grazing altogether depends on the nutrient content of the grass in your region as well as the sensitivity of each patient. In general, it is wise to not allow PPID patients to graze free choice, and particularly when grass is lush and abundant. An important question to ask is how much feed are you feeding daily? It is important to answer this question using the WEIGHT of your feeds (hay, concentrates, pellets), not the VOLUME. In general, a horse needs about 2% of his/her body weight in dry matter feed per day. This equates to about 20-25 pounds of hay, or other forage, daily for a 1000 pound horse. Most horses are not fed this much hay, and a pelleted feed or other concentrate is used to provide other nutrients and calories. Whether to offer only hay to your horse depends on the nutrient content of the hay, as well as the ability to find the supply of hay you would need. In a very general sense, in horses diagnosed with PPID, those with recurrent bouts of laminitis, and those suspected of having PPID or insulin resistance (IR), we recommend that they be fed feedstuffs with low non-structural carbohydrate (NSC) content. Although IR is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. The possible mechanisms behind IR are numerous and can be discussed with your veterinarian. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods, which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise, as you are doing. Although more scientific research is needed, it is believed that NSC can negatively affect IR-susceptible horses by (1) providing excessive sugar intake and thus worsen IR, as occurs in diabetic people, and (2) large amounts of NSC may change the large intestine’s bacterial flora; this is thought to lead to greater production of laminitis “trigger-factors.” Forage analysis of your hay is strongly encouraged to accurately determine the NSC content of your hay (check out Dairy One Forage Laboratory). NSC content below 12% is suggested for IR horses and ponies. Also, if more calories are needed, fat sources, such as vegetable oil or rice bran, are excellent choices instead of grains and feeds with high molasses content. Higher fiber content in the daily diet is also encouraged. This can be found in beet pulp and many commercially produced pelleted feeds. Another good source of basic information about feeding PPID and IR patients and feed choices is the website: www.safergrass.org.

In your situation, with your horse’s tentative PPID diagnosis, limiting NSC intake is likely a good idea for him, as it may help maintain good insulin sensitivity. It is important too that his diet contains adequate vitamin and mineral content. I recommend discussing IR further with your veterinarian, including testing for IR (resting insulin and/or combined glucose-insulin test). He/she can find some very informative IR information from the 2006 AAEP Annual Convention Proceedings.

Based on the long hair coat alone, the most likely explanation for this older gelding is Cushing’s syndrome. Based on several reviews of affected horses, a long, curly or wavy, hair coat is often the most common sign of Cushing’s syndrome. Other common signs of the disorder, also termed pituitary pars intermedia dysfunction (PPID), are excessive or inappropriate sweating, excessive water drinking and urination, intermittent bouts of laminitis, and chronic infections.

Many horses live for many years without a confirmed diagnosis or therapy, but medical treatment and regular health care may help this older guy enjoy an even happier older age. Whether to discuss this possibility with the owner is up to you. If you know the owner relatively well, it may be worth talking about the topic of PPID with him/her. Another possibility would be to ask a veterinarian at the barn to talk with the owner about these health issues.

These are all great questions about managing the diet of a horse with Cushing’s syndrome, or pituitary pars intermedia dysfunction (PPID). Rather than increase the Pergolide dose in response to spring’s more lush grass, I would suggest using a grazing muzzle on him so he consumes less of the rich, springtime grass. We recommend limiting the richer grasses because they tend to have higher non-structural carbohydrate (NSC) content. Although more scientific research is needed, it is believed that NSC can negatively affect PPID patients, and insulin resistance (IR) - susceptible horses, by (1) providing excessive sugar intake and thus worsen signs of PPID and/or IR, as occurs in diabetic people; and (2) large amounts of NSC may change the large intestine’s bacterial flora. This is thought to lead to greater production of laminitis “trigger-factors.” You are fortunate that laminitis has not been a recurrent problem for your horse. However, with his PPID diagnosis, limiting NSC intake is likely a good idea for him, as it may help maintain good insulin sensitivity as he ages. It is important too that his diet contains adequate vitamin and mineral content.

Your gelding’s muscle mass loss is a common sign of advancing Cushing’s Disease, so I would also suggest consideration of repeating the PPID diagnostic tests (dexamethasone suppression test, ACTH measurement, for example). Some horses do require increased Pergolide doses as they age and the disease progresses in the pituitary. Depending on recheck blood tests, your veterinarian may recommend increasing the Pergolide dose. This would be prescribed every day throughout the year, not just when richer grass is available. Also, if your gelding’s organ function is still good, increasing his crude protein content in his daily diet may help to improve his condition and muscle mass. Based on his diet description, I suspect that your gelding is not getting adequate protein intake on a daily basis. Geriatric horses generally require more protein than an average adult horse on a maintenance diet. The product, Hard Keeper, which you use appears to provide good fat sources, but not in a large enough quantity to provide a large source of calories. Also, having a forage analysis of your “mediocre” fescue hay will help you and your veterinarian design a good feeding program, because it will tell you how much protein content is provided by your hay. A combination of hay, limited grazing and pelleted feed should provide the majority of his calories and nutrients. You may need to alter the amounts of your current feedstuffs. Again, I suggest discussing these options with your veterinarian, but other protein source choices include soybean meal, as well as other commercial feeds with higher protein contents (crude protein percent ranging from 12-15 percent). Your veterinarian can find some very helpful information regarding diagnosis and long-term management of PPID-patients in the 2006 AAEP Annual Convention proceedings.

Because Cushing’s syndrome, or pituitary pars intermedia dysfunction (PPID), is thought to be a progressive disease process, I would suggest consideration of repeating the PPID diagnostic tests with your gelding. Unlike cancer, PPID is not thought to go into remission status. Rather, the horse’s outward signs may fluctuate over time, but the pituitary gland abnormalities remain and typically progress with age. Testing options include the dexamethasone suppression test and measurement of ACTH. ACTH is one of many hormones that are over-produced by horses with PPID. Most horses and ponies with this diagnosis do maintain themselves better when treated with daily pergolide. Also, some horses do require increased pergolide doses as they age and the disease progresses in the pituitary. Depending on recheck blood tests, your veterinarian will likely recommend using pergolide again, and on a continuous basis. Your veterinarian can find some very helpful information regarding diagnosis and long-term management of PPID-patients in the 2006 AAEP Annual Convention proceedings.

Based on current knowledge, we do recognize various breeds as being more likely to develop pituitary pars intermedia dysfunction (PPID - a.k.a Cushing’s syndrome) or insulin resistance (IR), but management as a distinct cause of these disorders has not been identified.

Regarding your questions about Cushing’s Disease in “younger” horses, it has been described, although it is far more common in aged horses, i.e. late teenagers or older. That being said, with proper diagnostics and management, horses diagnosed with PPID can lead very active and athletic lives. I emphasize diagnostics because we do know that our common tests for PPID are not always correct. Recent studies have shown that ACTH measurements vary significantly depending on the time of year, and that the dexamethasone suppression test can vary considerably in an individual horse. That said, a horse which exhibits the signs you described – mild laminitis, long haircoat, excessive drinking, are all classic signs of PPID.

Although insulin resistance (IR) is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods, which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise. Testing for IR can be done by your veterinarian. He/she can find further details in the AAEP Annual Convention proceedings from 2006.

As for your PPID horses’ management, focusing on consistent pergolide therapy, regular foot/hoof care, proper diet and regular exercise will help your horses continue to thrive. Diet suggestions are based on keeping your horses’ blood sugar as consistent as possible and, thus, insulin levels as even as possible. This is thought to be best achieved by feeding forage with low NSC content. This is typically found in grass hays. To determine the actual NSC content of your hays, I suggest having forage analysis performed (Dairy One Forage Laboratory is an option). It is suggested to feed hay with NSC content below 12 percent to PPID and/or IR-affected horses. Also, for horses with PPID, avoidance of all sweet feed is recommended, even that one cup a day you use to provide the daily supplements. An alternative is to use a small amount of moistened beet pulp. Use of vitamin and mineral supplements, as you currently do, is often needed especially when hay soaking is done. The water can leech out important nutrients. For specific advice on formulation of your PPID horses’ diets, I suggest discussing these and other questions with your veterinarian. You might also consider a consult with a veterinary nutritionist. Regular exams for your horses with PPID, including physical exam, basic blood work, as well as possible recheck PPID testing, and regular hoof care, can help your horses live long, productive lives.

Deciding on the “best” diet for your horse is a challenging task. Your horse’s dietary needs may change over time as well. Horses with Cushing’s disease, or more appropriately Pituitary Pars Intermedia Dysfunction (PPID), exhibit a variety of signs. You listed some of the more common ones. Although insulin resistance (IR) is not identified in all horses with PPID, it can be an associated endocrine problem for many equine PPID cases. Insulin resistance is a term used to describe the condition in which various body tissues fail to respond appropriately to insulin. In a classic scenario, the individual has both abnormally high blood sugar and blood insulin concentrations. The possible mechanisms behind IR are numerous and can be discussed with your veterinarian. A major concern with IR is that it appears to be linked to pasture-associated laminitis in horses and ponies. Thus, when IR is identified or suspected in a horse, veterinarians often suggest methods which may help a horse’s insulin sensitivity. This typically includes diet changes and an increase in regular exercise. An important recommendation is to feed grass hay or other feed sources, which are low in non-structural carbohydrates (NSC).

Although more scientific research is needed, it is believed that NSC can negatively affect IR-susceptible horses by (1) providing excessive sugar intake and thus worsen IR, as occurs in diabetic people, and (2) large amounts of NSC may change the large intestine’s bacterial flora; this is thought to lead to greater production of laminitis “trigger-factors.” These theories are the reason why discussion of low-NSC feedstuffs is so common. Forage analysis of your hay is strongly encouraged to accurately determine the NSC content of your hay (check out Dairy One Forage Laboratory). NSC content below 12 percent is suggested for IR horses and ponies. Also, if more calories are needed, fat sources, such as vegetable oil or rice bran, are excellent choices instead of grains and feeds with high molasses content. Higher fiber content in the daily diet is also encouraged. This can be found in beet pulp and many commercially produced pelleted feeds.

In your situation, fortunately, chronic laminitis has not been a problem for your gelding. However, with his PPID diagnosis, limiting NSC intake is likely a good idea for him, as it may help maintain good insulin sensitivity. It is important too that his diet contains adequate vitamin and mineral content. I recommend discussing IR further with your veterinarian, including testing for IR (resting insulin and/or combined glucose-insulin test). He/she can find some very informative IR information from the 2006 AAEP Annual Convention proceedings.