Anti-Müllerian hormone, testicular descent and cryptorchidism

Abstract

Anti-Müllerian hormone (AMH) is a Sertoli cell-secreted glycoprotein involved inmale fetal sex differentiation: it provokes the regression of Müllerian ducts, whichotherwise give rise to the Fallopian tubes, the uterus and the upper part of thevagina. In the first trimester of fetal life, AMH is expressed independently ofgonadotropins, whereas from the second trimester onwards AMH testicularproduction is stimulated by FSH and oestrogens; at puberty, AMH expression isinhibited by androgens. AMH has also been suggested to participate in testiculardescent during fetal life, but its role remains unclear. Serum AMH is a wellrecognized biomarker of testicular function from birth to the first stages ofpuberty. Especially in boys with nonpalpable gonads, serum AMH is the mostuseful marker of the existence of testicular tissue. In boys with cryptorchidism,serum AMH levels reflect the mass of functional Sertoli cells: they are lower inpatients with bilateral than in those with unilateral cryptorchidism. Interestingly,serum AMH increases after testis relocation to the scrotum, suggesting that theectopic position result in testicular dysfunction, which may be at least partiallyreversible. In boys with cryptorchidism associated with micropenis, low AMH andFSH are indicative of central hypogonadism, and serum AMH is a good marker ofeffective FSH treatment. In patients with cryptorchidism in the context ofdisorders of sex development, low serum AMH is suggestive of gonadaldysgenesis, whereas normal or high AMH is found in patients with isolatedandrogen synthesis defects or with androgen insensitivity. In syndromicdisorders, assessment of serum AMH has shown that Sertoli cell function ispreserved in boys with Klinefelter syndrome until mid-puberty, while it is affectedin patients with Noonan, Prader-Willi or Down syndromes.