Ruminant thyroid disease in practice In clinical practice, the most common thyroid disease in ruminants is hypothyroidism. A characteristic symptom of thyroid disease is the presence of goitre. An enlarged thyroid gland in seen in both hypo- and hyperthyroidism. Diagnosis of thyroid diseases is based on a clinical examination and laboratory testing (T4, T3 and TSH hormones). Comprehensive treatment of thyroid diseases includes dietary management, supplementation of iodine and administration of thyroxine-containing medications.