by: Les Sellnow
July 01 1999, Article # 352
A properly functioning thyroid gland is highly important to a horse's good health. That much is easy. From there it gets more difficult and complex. Knowing when the thyroid gland is in a state of dysfunction is not easy to determine.
The problem or issue before the house, at least one researcher believes, is that the thyroid gland, in a number of instances, might be innocent of any wrongdoing and that some treatment protocols are creating problems they are seeking to remedy. That researcher is Nathaniel T. Messer IV, DVM, of the University of Missouri in Columbia. At the December, 1998, AAEP meeting in Baltimore, Messer, who conducted a good deal of research on the thyroid gland, also presented a paper that detailed the results of a study at two central Kentucky Thoroughbred farms involving low hormone levels in mares and foals.
Messer summarized the complexity of the thyroid debate with this opening statement in his presentation at Baltimore:
"There is a wide spectrum of equine clinicians with varying beliefs about thyroid disease, ranging from those who believe thyroid disease is common and often diagnose it in horses who are infertile, have laminitis, or race poorly, to those who do not even believe it exists.
"In adult horses, thyroid dysfunction is generally felt to be uncommon, and while it has been associated with a variety of clinical signs, a definitive diagnosis is often difficult. One of the reasons for this is that many endogenous and exogenous factors can affect thyroid function and sometimes test results. Serum levels of thyroid hormones vary over a wide range, and low baseline levels may be misleading, which may result in many euthyroid (normal) horses being diagnosed as hypothyroid...
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