Feline hyperthyroidism -An overview

Thyrotoxicosis is a clinical condition resulting from excessive production and secretion of thyroxine and triiodothyronine. Feline hyperthyroidism is always the result of primary autonomous condition with benign tumor appears to be much more common than carcinomas. Most hyperthyroid cats have variety of clinical signs that reflect multiple organ dysfunction. Most frequent sign includes polyphagia, weight loss, heat intolerance, apathy, diarrhea and also associated with enlargement of one or both thyroid lobes. Hyperthyroidism can be diagnosed based on clinical signs, palpable thyroid nodules, laboratory findings and hormonal assay. Laboratory findings include increase serum enzymes ALT and AST levels. Measurement of random basal serum total T₄ concentration has been extremely reliable in identifying the cats with hyperthyroidism. Serum tT₄ concentration is more reliable than basal serum T₃ levels. If serum hormones fail to confirm thyrotoxicosis then radionuclide thyroid scan should be considered. I¹³¹ and 99MTc (Pertechnate) provide excellent thyroid images. Thiouracil, Propyl thiouracil (PTU) and Methimazole are drugs used for treatment of thyrotoxicosis. Surgery must be approached as elective procedure and last resort.