Horses' Thyroid Disease

What Is the Thyroid?

• The thyroid is a small gland that produces and regulates thyroid hormones. These hormones aid in a variety of body functions, which is why thyroid problems can result in a variety of symptoms.

Hypothyroidism

• Hypothyroidism, or low thyroid function, leads to a lack of energy or weakness. Sudden changes in weight and problems with fertility have also been linked to hypothyroidism. Other conditions like laminitis, loss of coat condition and tendon problems in young horses can also be indicative of hypothyroidism.

Hyperthyroidism

• Hyperthyroidism, or an overactive thyroid, is very rare in horses and is usually only found when tumors of the thyroid are present. Symptoms can include excitability or nervous behavior. Horses with hyperthyroidism may exhibit an inability to sweat or might be thin despite a healthy appetite.

Diagnosis

• Thyroid disease in horses is diagnosed by taking several blood samples for evaluation. Periodic samples are taken due to the natural fluctuations of thyroid hormones in the horse's body. Taking multiple samples will ensure accuracy.

Treatment

• Supplementation of thyroid hormone is sometimes prescribed for horses with hypothyroidism. Thyroid hormone supplementation should be approached with caution, though, as additional hormones can cause further imbalances within the body. In the case of hyperthyroidism, the treatment is usually removal of a thyroid tumor. Regardless of the type of thyroid disease, it is important that the horse have quality grain and hay free of harmful chemicals. Dietary iodine is especially important in horses with thyroid problems. Iodine is essential for production of thyroid hormones, so a diet balanced in iodine helps the thyroid gland to function normally.