Comparative studies in two cases of testicular feminization syndrome, one with and the other without the fluorescent distal band q12 of the Y.

In two patients with testicular feminization syndrome, one Yq12-positive and the other Yq12-negative, we compared phenotype, gonadal histology and ultrastructure, in vivo steroid response of the testes to the administration of exogenous gonadotropin during adrenal suppression, and of the adrenal gland to ACTH. The assumption that the constitutive Y heterochromatin could function as a regulator of steroid biosynthesis and metabolism, with or without effect at other levels, was not firmly supported by the observations reported here. However, further studies along this line may help elucidate the biologic role of this portion of the Y chromosome in humans.