[Serologically detected HY antigen and its regulation]

The serologically detected, male predominant s HY Ag is a surface glycoprotein. The structural gene would be located on the 6th chromosome and regulated by gonosomal genes. The presence of testes (or testicular remenants) is linked to the s HY antigen expression in most abnormalities of sexual differentiation. However, the basal s HY Ag value is sometimes increased in the absence of any testicular tissue, as in virilized females (21-hydroxylase deficiency, idiopathic or ovarian hirsutism). Homogametic sex s HY Ag may increase to heterogametic sex values under the action of androgens in mammals and that of oestrogens in birds.