Menstrual bleeding, hormones, and the menopausal transition

The perimenopause represents a time of great variability in reproductive ho rmone dynamics and menstrual cycle characteristics, but age-related changes begin prior to this. These changes include a gradual increase in follicle stimulating hormone (FSH) levels, a gradual shortening of mean cycle length , and a decline in the number of ovarian follicles. The onset of perimenopa use is thought to occur with the first break in menstrual cycle regularity With the onset of cycle irregularities, hormone concentrations exhibit larg e increases in variability and unpredictability, rather than following a gr adual trend with the approach of menopause, the final menstrual period. Abr upt spikes in gonadotropins and considerable fluctuations in estradiol and inhibin levels have been observed. Variability is the norm in the perimenop ause, with hormonal fluctuations contributing to the visible signs of menst rual cycle and bleeding irregularities. To date there is no single endocrin e indicator to serve as an adequate marker of menopausal status. This paper provides a review of research to date on patterns of reproductive hormones and menstrual bleeding during the menopausal transition. An understanding of such patterns can contribute to a better ability to distinguish "normal" transitional events from more serious pathology.