Effects of thyroidectomy and replacement therapy on the adrenal and testis of the bird myna, Acridotheres tristis.

Thyroidectomy in Myna, Acridotheres tristis, increased the levels of cholesterol, ascorbic acid and decreased the activity of the adrenal. The size and activity of the testis also decreased following thyroid removal. The weight of the two glands and activity of testis was not affected by 0.25 mg of 1-thyroxine. The chemical and histological changes of the adrenal were however reversed. It is suggested that thyroid deficiency leads to reduced output of the trophic hormones from the adenohypophysis of the bird resulting in decreased size and activity of the gonad and of the adrenal.