Abstract
The perimenopause represents a time of great variability in reproductive hormone 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 perimenopause is thought to occur with the first break in
menstrual cycle regularity. With the onset of cycle irregularities, hormone concentrations
exhibit large increases in variability and unpredictability, rather than following
a gradual trend with the approach of menopause, the final menstrual period. Abrupt
spikes in gonadotropins and considerable fluctuations in estradiol and inhibin levels
have been observed. Variability is the norm in the perimenopause, with hormonal fluctuations
contributing to the visible signs of menstrual cycle and bleeding irregularities.
To date there is no single endocrine 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.
Keywords:
Menstrual cycle - menopause - perimenopause - reproductive hormones
