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553854 
Journal Article 
Physiology and endocrinology of the menopause 
Burger, HG 
2006 
1 
Medicine
ISSN: 0025-7974
EISSN: 1536-5964 
34 
1 
27-30 
The menopause is the permanent cessation of menstruation resulting from loss of ovarian follicular activity. Follicular granulosa cells produce estradiol and inhibins. An accelerated decline in follicle numbers occurs from about age 38 years, and the major initial change underlying the menopause is a selective, gradual decline in inhibin B, the major regulator of follicular phase follicle-stimulating hormone (FSH). It is produced by the granulosa cells of antral follicles during the early follicular phase. The inhibin B decline leads to increased FSH, which can maintain and even increase estradiol production for some years. Onset of menstrual irregularity after previously regular cycles marks the onset of the menopausal transition, when there is a substantial decline in inhibin B, with maintenance of estradiol. Anovulatory cycles increase as menstrual irregularity is established. The late menopausal transition is marked by 60-90 days of amenorrhoea and frequent prolonged and often anovulatory cycles. Estradiol levels decline and FSH is raised, but their concentrations vary considerably; measurements are of limited diagnostic value. At the time of the final menses, estradiol levels on average are 50% of those at mid-reproductive age; FSH is about 50% of the elevated concentrations finally reached postmenopausally. There is thus a profound decline (about 90%) in estradiol in the 3-4 years surrounding final menses, and this results in menopausal symptoms and bone loss. Testosterone levels decline by about 50% during mid-reproductive life, but show no significant change during the menopausal transition and in the early postmenopausal years. 
HRT; menopause; follicle-stimulating hormone; inhibin; estradiol; testosterone