THYROID IN AVIAN REPRODUCTION

Annual gonadal size and activity cycles of the nonmigratory Indian finches, viz: Lal Munia (Estrilda amandava) and Spotted Munia (Uroloncha punctulata), run parallel with the body weight cycles and are inversely related with the thyroid activity cycles. Gonads are developed when thyroid activity is low and are reduced when it is high. Further, severe hypothyroidism (thyroidectomy) induces gonadal recrudescence to full development, which is then maintained; and hyperthyroidism (l-thyroxine) at low levels reduces the weight, and at moderately high levels the activity also, of the gonads of adult normal and thyroidectomized birds during the breeding phase. It is suggested that changes in thyroid activity influence the output of the gonad-stimulating hormones from the adenohypophysis, which in turn regulate the annual and body weight cycles of Lal and Spotted Munia. © 1969.