Effects of mammalian hypophyseal hormones: gonadotropins, thyrotropin and adrenocorticotropin, on the embryonic development of 8-days chick embryo gonads.

When injected into chick eggs on the 8th day of incubation, gonadotropins (FSH + LH) were shown to stimulate the gonadal development on the 20th day of embryogenesis in both sexes. An increase in the testicular weight, in the seminiferous cord diameter as well as in germ and Sertoli cell number was observed in males. Similarly an increase in ovarian weight, in ovarian width, in cortical thickness and in the number of oocytes was reported in females. By contrast, thyrotropin (TSH) and adrenocorticotropin (ACTH) caused a noticeable decrease in gonadal development in both males and females as compared to the controls or to the gonadotropin-treated groups. It is concluded that the gonads of 8 days chick embryo have the capacity to respond to gonadotropic stimulation and not to the other hypophyseal hormones (TSH or ACTH). This suggests the possibility that at this early stage (8 days of incubation) the external specific hormone could induce its future hormone receptors.