Anti-Müllerian hormone: a new marker for ovarian function

Abstract

This review article provides a clear overview of anti-Mullerian hormone (AMH) and its use as a marker of ovarian function, especially in the fields of in vitro fertilization (IVF) and polycystic ovarian syndrome (PCOS). In the ovary, the granulosa cells of pre-antral and small antral follicles expressAMH; concentrations diminishwith increasing follicle size and stop at the follicle-stimulating hormone (FSH)-dependent stage. AMH has an inhibitory effect on the recruitment of primordial follicles and affects the sensitivity of follicles to FSH. Studies in vitro and on AMH null mice, covered in the article, have shown thatwithoutAMHmore primordial follicles are recruited into the growing pool, exhausting the primordial pool earlier. Furthermore, these studies show the absence of AMH reduces the follicle FSH threshold, allowing more follicles to grow and enter the next ovulation cycle at lower concentrations of FSH. Ovarian aging is marked by the size (and decline) of the primordial follicle pool, direct measurement of which is impossible. As the number of growing follicles indirectly indicates the primordial follicle pool size, consequently a marker expressed by thegrowing follicles shouldalso reflect the sizeof theprimordial folliclepool.AMHistherefore showingpromiseasamarker of ovarian reserve as it is expressed by growing follicles and can be measured in serum. Unlike other biochemical markers, changes in serum concentrations of AMH occur early in ovariandeclinebeforeany irregularities in thecyclearedetected; this would be of particular use in IVF treatment. Poor responders to the administration of exogenous gonadotrophins have poor pregnancy outcomes; they could be detected before entering an IVF programme. Conversely, AMH could be used to detect patients with a good ovarian reserve who would otherwise be excludedon thebasis of theirage.Oneparticularadvantage of AMH is that only one sample is required, which can be taken at any point in the menstrual cycle. The review article continues with AMH as a marker of ovarian dysfunction. In PCOS the defective selection of follicles for ovulation leads to an accumulation of small antral follicles, which are the main producers of AMH. A two to three-fold increase in the number of growing follicles is reflected by a similar two to three-fold increase in AMH concentrations. Also PCOS follicles appear to produce more AMH per follicle than their non-PCOS counterparts. Therefore, AMH could potentially become a marker for PCOS, though much more research needs to be done.