Premenopause: The period before MENOPAUSE. In premenopausal women, the climacteric transition from full sexual maturity to cessation of ovarian cycle takes place between the age of late thirty and early fifty.Perimenopause: The transitional period before and after MENOPAUSE. Perimenopausal symptoms are associated with irregular MENSTRUAL CYCLE and widely fluctuated hormone levels. They may appear 6 years before menopause and subside 2 to 5 years after menopause.Menopause: The last menstrual period. Permanent cessation of menses (MENSTRUATION) is usually defined after 6 to 12 months of AMENORRHEA in a woman over 45 years of age. In the United States, menopause generally occurs in women between 48 and 55 years of age.