Q:Have you ever heard of a bilateral goiter (both the left and right sides of the thyroid gland are enlarged) in a horse? I have a 7-year-old Tennessee Walking Horse gelding. He has had a goiter all his life that has not caused any problems. After coming home from being away for a week, I noticed a second lump, and possible goiter, on his neck. My veterinarian checked the lump and said he has never seen or heard of a bilateral goiter. He is looking into it, and I thought I would research it also.

My boy is showing classic "human Grave's disease" signs, not that it has ever been seen in a horse.

Alycia Partei, Reno, Nev.


A: You indicated that this gelding is exhibiting clinical signs that are typical for Grave's disease in people. Grave's disease is an autoimmune condition in which the patient's thyroid glands are overactive and enlarged. Thyroid overactivity is referred to as hyperthyroidism and has been rarely reported in old horses (older than 20 years) affected with thyroid cancer. Grave's disease has never been reported in horses and hyperthyroidism has not been reported in such a young horse. Although you did not describe the observed symptoms for this horse, hyperthyroidism in old horses tends to be associated with excitability, sweating, weight loss, increased appetite, and hair coat abnormalities

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