In order to study the role of thyroid hormone in avian physiology, reliable methods for inducing sustained states of hyperthyroidism and hypothyroidism in the turkey were developed. Hyperthyroidism was established by administration of L-thyroxine (3 fig/ml) to the drinking water. Hypothyroidism was established either by the provision of a low-iodine diet and supplementation of the drinking water with .5% sodium perchlorate, or by the intravenous administration of an ablative dose (10 mCi) of 131 1". Clinical manifestations of hyperthyroidism and hypothyroidism were accompanied by high (10.1 ±1.4 Mg/dl) or low (.34 ± 0.04 Mg/dl) plasma concentrations of thyroxine, respectively, both significantly different from normal controls (.57 ± .08 Mg/dl; P<.05). Among the objective manifestations were striking differences in basal body temperatures in the hyperthyroid, normal, and hypothyroid groups: 41.0 ± .12 vs. 40.5 ± .06 vs. 39.8 ± .10 C, respectively (P<.002). Hyperthyroidism was also associated with decreased total serum lipids, cholesterol, and uric acid, whereas hypothyroidism was associated with significantly increased serum levels of cholesterol, uric acid, glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, lactic dehydrogenase, and creatine phosphokinase. The following serum parameters were similar among all groups of turkeys: calcium, phosphorus, blood urea nitrogen, creatinine, total protein, albumin, sodium, chloride, glucose, alkaline phosphatase, 7-glutamyl transpeptidase, triglycerides, bilirubin, and iron. Circulating catecholamine levels were also unchanged (14 to 23 nM) among the three groups of birds.
