Hyperthyroidism in cats

Hyperthyroidism, primarily due to functional thyroid adenoma, is the most common endocrinopathy of older cats worldwide. Even though the etiopathogenesis of feline hyperthyroidism is not yet fully understood, the four common therapeutic modalities that can be implemented individually or in combination for management are surgical thyroidectomy, radioactive iodine, pharmaceutical therapy and dietary therapy using a limited-iodine diet. Regular monitoring of a hyperthyroid cat is important to assess therapeutic efficacy, to detect iatrogenic hypothyroidism and to confirm comorbidities that become evident with resolution of the hyperthyroidism. Thyroid gland is an endocrine gland located at the neck area. In cats, this gland has two lobes connected by an indistinct isthmus. The functional unit of the gland is the thyroid follicle and the three hormones produced are triiodothyronine (T3), thyroxine (T4) and calcitonin. Secretion of T3 and T4 are regulated by the thyroid-stimulating hormone (TSH) and thyrotropin-releasing hormone (TRH) produced by the pituitary gland and hypothalamus, respectively. Ectopic or accessory thyroid tissueis relatively common in many species including cats and may be located anywhere from the larynx to the diaphragm. Hyperthyroidism is characterized by the overproduction of thyroid hormone and a subsequent increase in metabolic rate.

Key Words: Hyperthyroidism, Cats