Q: Are thyroid conditions common in horses?
A: Thyroid conditions in horses are discussed frequently, but seldom firmly diagnosed. In the equine the main problems we see with the thyroid gland are tumors, perhaps hypothyroidism, and occasionally inflammation. Foals are more susceptible to hypothyroidism than adult horses, usually from an Iodine deficiency. In fact, we may need to supplement more iodine than has been done in the past. Supplementation is often best done with kelp to enhance its absorption, with about 2-3 mg per day as an approximate dose. We do not know the true optimum level at this time.
In general, the horse that we used to consider a classic hypothyroid case, the fat, cresty individual, we now recognize is Insulin Resistant (IR) and is best treated for IR. The true incidence of hypothyroid adult horses is probably negligible, except for some iodine deficient horses. Check your supplements carefully; iodine is in many supplements so it may not be deficient.
Q: So, how do you diagnose hypo- or hyperthyroidism?
A: With a blood test, thyroid stimulating hormone (TSH), T4 and T3 hormones can be measured. Low serum/blood levels of biologically active thyroid hormone define true hypothyroidism. If a horse is hypothyroid it is probably due to low levels of TSH rather than primary disease in the gland itself.
There are many difficulties with diagnosing hypothyroidism in horses. To begin with, there is a natural diurnal (variable) rhythm to the levels of thyroid hormones. Generally we collect blood samples when we come to your farm, so there is no standardization or repeatability to the sample collection. With the natural variation in T4 levels, one day the blood might be collected and it could look normal, the next time, it might look low.
Other factors affecting blood levels:
- the use of Phenylbutazone, aka Bute (very common)
- high carbohydrate or high protein diets
- high levels of zinc and copper
- stress or other factors that release glucocorticoids (natural body steroids)
- lack of food
- training and fitness levels
- eating endophyte fescue grass
Stress is a big unknown, since what one horse considers stress (staying in a stall, for example) might be little stress for another horse. Competing and traveling frequently, harsh training techniques, unfriendly stable/pasture mates all can be stressful, thus may affect thyroid blood levels.
Hyperthyroidism, while common in humans and cats, rarely if ever occurs in horses, and if it does, is usually associated with a tumor.
Q: How prevalent is thyroid cancer, and does it respond to alternative treatment?
A: Thyroid cancer does occur in horses, though it is not common. As with many cancers, it can be treated successfully with alternative medicine. Not all cancers respond well, and not all horses are capable of responding, but homeopathy, Chinese herbal medicine, antioxidants, therapeutic mushrooms (Maitake, Reshi, shiitake, etc.) and Noni powder all can help. A quick case example: a 33-year-old grade gelding was diagnosed with a large swelling in his thyroid gland, suspected to be cancer. It had been there for several years, but was getting larger. The area got infected and was drained. He was placed on a homeopathic remedy that fit his case, and after several weeks, a large grey mass of tissue came out of the drainage hole. When the wound healed, his thyroid swelling was gone and he lived happily until he was 38.
Harmany Equine Clinic, Ltd., www.harmanyequine.com
Holistic Horse: your guide to natural horse health