Role of thyroid and testicular hormones in the regulation of basal metabolic rate, gonad development, and body weight of spotted munia, Lonchura punctulata

Abstract Normal saline, l -thyroxine ( l -T 4 , 0.5 μg/bird/day), and testosterone (100 μg/bird/day) were administered separately to intact, thyroidectomized, and castrated spotted munia over a 30-day period and the effects on basal metabolic rate (BMR), gonads, and body weight were recorded. Thyroidectomy and castration decreased the BMR. l -Thyroxine increased the BMR of intact and thyroidectomized but not of the castrated birds. Testosterone had no effect on BMR of either the intact or of the operated birds. l -Thyroxine and testosterone both had no effect on regressing gonads but inhibited thyroidectomy-induced testicular development. Body weight increased in intact, testosterone-treated birds, and in thyroid-ectomized and castrated spotted munia. l -Thyroxine inhibited body weight gain only in thyroidectomized birds. It is suggested that the physiological actions of l -T 4 and testosterone depend on the gonadal status, thyroid activity, and nature of the thyroid-gonad relationship.