Effect of testosterone and thyroxine on corticosterone and transcortine plasma levels in different bird species.

Effect of testosterone and thyroxine on corticosterone and transcortine plasma levels has been investigated in photostimulated (18L--6D) Peking duck, domestic pigeon, Japanese quail and cock. In all these bird species corticosterone and transcortine plasma levels increased following castration, while restitution with testosterone decreased them in the castrated animals. Thyroidectomy and thyroxine supplements in thyroidectomized birds failed to influence plasma corticosterone and, apart from cock, transcortine levels. It is suggested that in case of high testosterone levels the effect of thyroid hormones on the function of the adrenal cortex can partly or completely be masked by the dominancy of the testocorticoid interrelation.