Endocrine Abstracts

Anti-mullerian hormone (AMH), is a member of the TGFbeta family of growth and differentiation factors. Also known as mullerian inhibiting substance, AMH plays an essential role during male sex differentiation, where it signals the regression of the mullerian ducts.

However, in the postnatal female AMH plays an important role in growth and development of ovarian follicles. In both rodents and women, AMH is expressed in primary follicles immediately after they have started to grow, i.e. after recruitment, whereas its expression ceases in follicles that have been selected for dominance. I will discuss several aspects of the roles of AMH in ovarian function as they have been studied in AMH null mice, cultures of neonatal ovaries and single follicles. The main conclusion of these studies is that AMH inhibits primordial follicle recruitment and AMH inhibits the growth stimulatory effects of FSH.

AMH signaling follows the general pattern as found in the TGFbeta family, i.e. intracellular Smad proteins are activated by AMH through a complex of a specific AMH type II receptor and generic type I receptors. In the Mullerian ducts AMH employs the BMP-like pathway, with the involvement of the type I receptors Alk2 and -3 and activation of Smads-1, -5 or -8. In the ovarian granulosa cells (KK1 cells), AMH uses the BMP-like pathway. In the postnatal developing ovary, quantitative PCR showed expression patterns consistent with AMH signaling through Alk2/Alk3 and Smad1/5.

In our further studies of AMH we have addressed the possibility that AMH may act as a marker of the size of the ovarian reserve in women. AMH serum measurements in healthy volunteer cyclic women and in patients undergoing IVF therapy showed that an excellent correlation existed between AMH levels, and the antral follicle count, and the success rate of IVF as determined by oocyte pickup.