Natural menopause is defined as the permanent cessation of menstrual periods, determined retrospectively after a woman has experienced 12 months of amenorrhea without any other obvious pathological or physiological cause. It occurs at a median age of 51.4 years in normal women, and is a reflection of complete, or near complete, ovarian follicular depletion, with resulting hypoestrogenemia and high FSH concentrations (figure 1). Menopause before age 40 years is considered to be abnormal and is referred to as primary ovarian insufficiency (premature ovarian failure). The menopausal transition, or perimenopause, occurs after the reproductive years, but before menopause, and is characterized by irregular menstrual cycles, endocrine changes, and symptoms such as hot flashes.
This topic will review the clinical features and diagnosis of the menopausal transition and menopause. The physiology and epidemiology of menopause, postmenopausal hormone therapy, and primary ovarian insufficiency are reviewed separately. (See "Ovarian development and failure (menopause) in normal women" and "Menopausal hormone therapy: Benefits and risks" and "Pathogenesis and causes of spontaneous primary ovarian insufficiency (premature ovarian failure)".)
The menopausal transition, or perimenopause, begins on average four years before the final menstrual period, and includes a number of physiologic changes that may affect a woman’s quality of life. It is characterized by irregular menstrual cycles and marked hormonal fluctuations, often accompanied by hot flashes, sleep disturbances, mood symptoms, and vaginal dryness [1-6]. (See 'Symptoms' below.) In addition, changes in lipids and bone loss begin to occur, both of which have implications for long-term health.
Virtually all women experience the menstrual irregularity and hormonal fluctuations prior to clinical menopause, up to 80 percent develop hot flashes (the most common menopausal symptom), but only 20 to 30 percent seek medical attention for treatment. (See 'Hot flashes' below.)
Much of the available information about the endocrine and clinical manifestations of the menopausal transition comes from a number of longitudinal cohort studies of midlife women [7-19], the largest of which, the Study of Women’s Health Across the Nation (SWAN), has followed a multiethnic, community-based cohort of over 3000 women ages 42 to 52 years for 15 years [7,12-14,16,17,20-29]. Based upon data from the cohort studies, a staging system was developed that is now considered to be the gold standard for characterizing reproductive aging from the reproductive years through menopause. The STRAW staging system (Stages of Reproductive Aging Workshop) includes definitions for the late reproductive years, the menopausal transition, perimenopause, menopause, and postmenopause (figure 2) . Although the STRAW system has been used primarily for women’s health research, it is helpful in the clinical setting for patients and clinicians for assessing fertility potential, contraceptive needs, and potential need for hormone therapy.