Naturally declining reproductive hormones: As you approach your late 30s, your ovaries start making less estrogen and progesterone — the hormones that regulate menstruation — and your fertility declines.
Surgery that removes the ovaries (oophorectomy): Your ovaries produce hormones, including estrogen and progesterone that regulate the menstrual cycle. Surgery to remove your ovaries causes immediate menopause. Your periods stop, and you're likely to have hot flashes and experience other menopausal signs and symptoms.
Chemotherapy and radiation therapy: These cancer therapies can induce menopause, causing symptoms such as hot flashes during or shortly after the course of treatment. The halt to menstruation (and fertility) is not always permanent following chemotherapy, so birth control measures may still be desired. Radiation therapy only affects ovarian function if radiation is directed at the ovaries.
Primary ovarian insufficiency: About 1% of women experience menopause before age 40 (premature menopause). Premature menopause may result from the failure of your ovaries to produce normal levels of reproductive hormones (primary ovarian insufficiency), which can stem from genetic factors or autoimmune disease. But often no cause of premature menopause can be found.
Courtesy: Mayo Clinic
