Modern Veterinary Practice, 1983. p.649-652.
Hyperthyroidism in cats can be caused by tumors (often malignant) or cranial mediastinal accessory thyroid tissue. Middle-aged cats with insidious onset of hyperactivity, rough haircoat, weight loss, polyphagia, polyuria and polydipsia are suspect. A bilateral cervical swelling between the larynx and thoracic inlet~ and ECG abnormalities may be seen. Normal feline thyroid h9rmone levels have not been established and fluctuate with time of day, age. breed, pregnancy status and use of various drugs. Elevated SGOT, SGPT and serum alkaline phosphatase levels may occur. Thyroidectomy is the best treatment but propylthiouracil can be used. Postoperative complications include hypothyroidism, hypoparathyroidism, recurrent laryngeal nerve damage and recurrence of hyperthyroidism.