Hypothyroidism in a scarlet macaw

Abstract

A diagnosis of hypothyroidism was confirmed by use of thyrotropin stimulation testing in an imported male scarlet macaw. Clinical signs included delayed molt; uniform, diffuse contour feather loss over the entire body; and excessive fat deposition over the legs and ventral portion of the abdomen. Clinical signs were associated with mild, non-regenerative anemia; mild leukocytosis; heterophilia; hypoalbuminemia; and hypercholesterolemia. Histologic examination of punch biopsy specimens from regions of feather loss revealed ortho- and parakeratotic hyperkeratosis of the epidermis and moderate, widespread vacuolar degeneration and necrosis in the follicular epithelium. The bird failed to respond to provocative thyrotropin stimulation testing. Treatment with L-thyroxine (0.2 micrograms/kg of body weight, q 12 h) resulted in normal feathering, elimination of fat deposits, and adequate serum thyroxine concentrations at 4 and 12 hours after treatment.