DEVELOPMENT OF AN EXPERIMENTAL-MODEL OF HYPOTHYROIDISM IN COCKATIELS (NYMPHICUS-HOLLANDICUS)

Hypothyroidism is a possible predisposing factor in a number of disord ers of companion psittacine birds. We developed and validated a thyroi d-stimulating hormone (TSH) response testing protocol for cockatiels ( Nymphicus hollandicus), using 0.1 IU of TSH/bird given IM, with blood sample collection at 0 and 6 hours after TSH, and a commercial radioim munoassay for thyroxine (T-4). This protocol was used to document a se asonal sex difference in stimulated T-4 values - females responded wit h higher T-4 values than those in males in summer- and a stress-induce d depression of baseline T-4 values was detected in a group of cockati els with normal TSH response. An experimental model for mature-onset h ypothyroidism in cockatiels was created by radiothyroidectomizing cock atiels with 3.7 MBq (100 mu Ci) of I-131/bird given IV. Induction of t he hypothyroid state was confirmed by baseline T-4 concentration, TSH response test results, thyroid pertechnetate scintigraphy, and gross a nd microscopic examinations. Classical signs of hypothyroidism (eg, hy percholesterolemia, obesity, poor feathering) were lacking or mild at 48 days after thyroid ablation.