A condition in which the ovaries stop working and menstrual periods stop before age 40. Natural menopause usually occurs around age 50. A woman is said to be in menopause when she hasn’t had a period for 12 months in a row. Early menopause can be caused by some cancer treatments, surgery to remove the ovaries, and certain diseases or genetic conditions. Also called premature menopause, premature ovarian failure, and primary ovarian insufficiency.