I recently uploaded a new lecture to our online education courses; Equine Metabolic Syndrome.  I worry a little that the while the subject matter is one that most of my readers and students should know, the name may be confusing. Do you know what Equine Metabolic Syndrome means? Do you know about Insulin Resistance and what it means for your horses and their health?  It's when an overweight or obese horse develops a condition related to the obesity. They have abnormal fat deposition, exercise intolerance (lethargic and out of shape) and can develop serious medical conditions like laminitis. It's a little bit like Type II Diabetes in humans, but not close enough to use the same nomenclature (cause that would make it too easy for all of us).  While its something that has been going on in horses for as long as we’ve been putting them in stables and supplementing their feed but its something the scientific community has only been investigating for the last handful of years. And because the syndrome is old but the research is new, there is a lot of misinformation out there about why horses are fat and what we can do to fix it. One of the myths I have the hardest time debunking is that of Hypothyroidism. When people tell me their horse is hypothyroid I think of that line from A Princess Bride, “You keep using that word. I do not think it means what you think it means.” So let me tell you the schpeal that I give clients and other vets who call me for advice.

Hypothyroidism in a dog.
Back in the day, well not too long ago, people would notice that they had a horse that had become overweight and lethargic and they wanted to know why. In people and in dogs hypothyroidism is a real, documented disease and is somewhat common. Humans with thyroid dysfunction are fatigued, weak, irritable and gain weight, or have trouble losing weight. Dogs will become dull and listless, reluctant to engage in their normal activities and will gain weight despite no change in appetite or feedings. So it would only make sense that if your horse was now dull and pudgy that hypothyroidism would be the answer. So we started testing horses thyroid hormone levels and guess what? Sometimes they were low. ">Problem solved!!!  And thus hypothyroidism was blamed for a variety of equine problems such as obesity, laminitis, anhidrosis (inability to sweat), recurrent rhabdomyolysis (tying-up) and poor fertility.  But here’s the problem with that theory…. Thyroid hormone levels that we measure in the blood may not tell us about true thyroid function. And who cares what the numbers from the lab say if the thyroid gland itself is functioning properly and doing its job to aid in growth and regulation of metabolism? We also know that certain medications (Bute & dexamethasone), strenuous exercise and diets high in energy, protein, zinc and copper will falsely alter the levels of circulating hormones in the bloodstream. The only way to know about how the thyroid functions is to perform thyroid function tests, which are rarely done in the field because the medications needed to stimulate the thyroid (to prove to us that its working) are not readily available. But when horses that are showing the “classic” signs of hypothyroidism, and have low thyroid hormone levels are tested for true thyroid function, they are found to be normal. Researchers have even tried to prove this association by removing horse’s thyroid glands to see what happens. Well what doesn’t happen is they do not become obese and they do not develop laminitis.

“But I don’t understand!” you say. “I had a hypothyroid horse and we treated her and she got better! Was my vet wrong?” Well, yes and no. For all those years, we have been treating your horses correctly, using all of the knowledge that we knew at the time, but we were doing it for the wrong reasons. It has only been within the last few years that the veterinary community has come to define Equine Metabolic Syndrome. EMS is an endocrine disease of horses that is characterized by insulin resistance, meaning your horse’s cells don’t respond to insulin they way they should and the energy (glucose) they consume can’t be metabolized properly. It’s similar to Type II Diabetes in humans, in that it is often a result of obesity, rather than a cause. Some horses are more predisposed to being overweight, “easy keepers.” Obesity leads to insulin resistance, which in turn makes weight loss even harder to achieve. Horses with EMS are more prone to episodes of laminitis because of alterations in glucose and insulin in their blood streams. Many “hypothyroid” horses that have normal thyroid function will test positive for EMS and insulin resistance.

“So why does treating with thyroid medication make these horses better if they don’t have a thyroid problem?” you say. Excellent question! Well thyroid supplementation causes an increase in metabolism. By increasing the horse’s metabolism they are able to loose weight and correct their insulin resistance. It works so well that researchers are now recommending treating these types of horses with a much higher dose of thyroid supplementation, a “supraphysiologic dose.” So while we have been doing the right thing all along, we only now understand why it was working. It is important to understand one other big difference. True hypothyroidism, in dogs and people, will require life long treatment. Horses who have been successfully treated for EMS do not, and unnecessary treatment with thyroid supplementation over extended periods of time is not only a waste of money, but also a potential health risk.

   So if you have a horse that is slow, sluggish and fat, or one that has been previously diagnosed as hypothyroid, learn more about Equine Metabolic Syndrome by taking our online course and talk to your vet about what you can do to test and treat this very common condition.

Have you ever wondered what the difference is between the brand name veterinary products your veterinarian sells and the products in catalogues and tack stores that claim to be exactly the same but cheaper and without a prescription? Most people think of these as generics, over the counter versions of these medications much like we have generic and OTC versions of our human products like allergy medications and painkillers. But this is may not be true and the distinction between prescription, generic and a compounded drug is very important to understand. A brand named prescription medication is one that is FDA approved and comes with all the bells and whistles of a newly developed product. Once this new product’s patent expires, other companies can produce the same drug, using the same formula, same dosage, same ingredients and same form, but usually at a lower cost. Generic medications go through the same rigorous FDA approval process to assure efficacy and safety before they are on allowed on the shelves.

To “compound” a medication is to mix drugs to create a product that is not commercially available (most common in vet med) or to change the delivery (pill to liquid) or flavor (most common in pediatric med). Compounding pharmacies are mostly self-regulated and have little to no external oversight, meaning no one is making sure their products contain what the label claims. This is different from a “generic” medication, which has FDA approval and regulations.

Prescribing generic forms of medications is completely legal because the FDA has approved these products. In veterinary medicine the FDA only allows for compounding of drugs that are not commercially available in an FDA approved form. Prescribing and using a compounded drug that is commercially available, besides being against the law, may not give you the results you are looking for, or worse, can be dangerous.

An FDA study showed that 34% of compounded drugs do not meet the potency standards compared to their approved counterparts, and most of these had less than 70% of the active ingredient the label claimed!!!  Another recent study presented at last year’s AAEP Convention compared compounded omeprazole products (lower cost versions of Gastrogard for the treatment of ulcers). The compounded forms had less than 63% of the label claim of omeprazole. Meaning, you’d have to give almost two tubes of compounded omeprazole to get the same effect as a single tube of Gastrogard! Additionally the materials used to make these medications do not always come from high quality sources or FDA approved manufacturers making their safety and stability questionable as well.

One of the most common examples of proper compounding in veterinary medicine is pergolide, the medication used to treat Cushing’s Disease in horses. Years ago there was an FDA approved human formulation of the drug that we were able to give to our horses. But more recently they had stopped making this medication for humans and we were forced to use a compounded form to continue treatment on these Cushing’s cases. Because these were not regulated formulations there was always a question as to whether or not there was the right amount of drug in the compound. Was the horse not responding because the diagnosis was wrong or the condition was worsening? Or was it just that we wanted to give 1mg of drug per day but the formulation only contained 0.5mg? Often times finding the right dose for each horse was a guessing game. Thankfully a new FDA-approved equine formulation of pergolide is on the market- Prascend® (Boehringer Ingelheim). Though many people have become used to using the compounded powder or suspension, veterinarians will be switching over to the approved product because we can be confident that it is efficacious and safe for our patients.

While we will always need to compound some drugs in order to have the full arsenal available to keep our animals healthy, when we do compound, we closely research the company and often employ outside labs to verify the concentration and purity.  So talk to your veterinarian about compounded medications and beware of online companies offering compounded versions of medications at reduced prices (especially if it is a prescription med and they do not ask for a script!) because you may not be getting what you need!