EMBRYOLOGY AND ENDOCRINOLOGY OF GENITAL DEVELOPMENT

In the human male fetus, testes develop by the 7th week and begin to s ecrete two hormones: and-mullerian hormone (AMH) induces the regressio n of mullerian ducts, the anlagen of the uterus, fallopian tubes and u pper vagina, upon binding to a specific membrane receptor, whereas tes tosterone induces the differentiation of the wolffian ducts into the e pididymes, vasa deferentia and seminal vesicles. in some target tissue s, testosterone is converted to dihydrotestosterone, which is responsi ble for masculinization of the urogenital sinus and external genitalia . Both androgens act upon binding to the same nuclear receptor. In the absence of AMH and androgen action, for example in the female or in a bnormal male differentiation, the internal and external genital primor dia differentiate following the female pathway, even in the absence of ovaries. In males, an impaired function of the AMH-dependent pathway results in the persistent mullerian duct syndrome, a disorder characte rized by the presence of uterus and fallopian tubes in otherwise norma lly virilized boys. Several mutations found in the AMH and AMH-recepto r genes explain the pathophysiology of this syndrome.