Equine hyperthyroidism

Veterinary advice should be sought before applying any treatment or vaccine.

Equine Hyperthyroidism

Equine Hyperthyreosis, Overactive Thyroid In Horses

Equine hyperthyroidism is an endocrine condition in which the thyroid gland makes too much thyroid hormone. The condition is somewhat uncommon in horses and is caused by exposure to excessive amounts of iodine-containing compounds (leg paints, povidone-based products, counterirritants, drugs, expectorants), inflammation of the thyroid, and noncancerous growths of the thyroid gland or pituitary gland.


Muscle tremors
Increased sweating
Hair loss
Heat intolerance
Weight loss
Hyperactive behavior
Increased appetite
Increased thirst
Enlargement of the thyroid gland


  • History
  • Clinical signs
  • Physical exam
  • Biopsy
  • T3-Suppression test


Elimination of exposure to iodine-containing compounds
T3twice daily for 4 days through IM
Glucocorticoid administration
Antithyroid therapy with potassium iodide


Variable, depending on the cause and response to treatment

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