Thyroid Diseases.

Thyroid hormones in horses fluctuate with factors like time of day, diet, activity, or medications. True hypothyroidism is rare in adults, and other causes for the observed clinical signs, such as equine metabolic syndrome, should be considered. Hyperthyroidism can occur in older horses and is sometimes associated with clinical signs requiring surgical treatment. In neonatal foals, distinct forms of hypothyroidism are associated with dysmaturity and can be life-threatening. While thyroid supplementation can help in managing equine metabolic syndrome, inappropriate use can impair athletic performance.