Effect of thyroxin on the gonad and body weight of Spotted Munia, Uroloncha punctulata

Abstract

Low doses of l‐thyroxin promote feather regeneration and lead to significant reduction in the mean weight of the gonad of adult normal and thyroidectomized Spotted Munia, Uroloncha punctulata, in the breeding phase. At moderately high doses of thyroxin complete molting occurs, and the mean weight of the gonoduct is also significantly reduced. The effect of l‐thyroxin increases as the duration of administration is increased. There is practically no difference between the response of normal and thyroidless birds. It is suggested that whereas the effects of l‐thyroxin on the plumage are by way of body metabolism, those on the gonad, gonoduct and body weight are due to a direct influence on the output of the gonad‐stimulating and growth‐promoting hormones from the adenohypophysis. Copyright © 1968 Wiley‐Liss, Inc., A Wiley Company