Clinical meaning
Menopause is defined as 12 consecutive months of amenorrhea due to permanent cessation of ovarian follicular activity, occurring at a median age of 51 years. The perimenopause (menopausal transition) begins 4-8 years before final menstrual period with fluctuating estradiol levels and irregular cycles. Declining ovarian follicle reserve leads to decreased inhibin B production, releasing FSH from negative feedback inhibition. Rising FSH levels are characteristic of perimenopause (FSH > 25 IU/L on day 2-3 of cycle). Complete follicular depletion results in sustained estradiol levels < 73 pmol/L and FSH > 40 IU/L. Estrogen deficiency produces vasomotor symptoms (hot flashes, night sweats) through thermoregulatory dysfunction in the hypothalamus, genitourinary syndrome of menopause (GSM: vaginal atrophy, dyspareunia, urinary symptoms), and accelerated bone loss (2-3% annually in the first 5-7 years post-menopause). Menopausal hormone therapy (MHT) remains the most effective treatment for vasomotor symptoms.