In the Western world, a woman's last period occurring between the ages of 55 to 60 is known as a "late menopause". An "early menopause" is defined as having the final period somewhere between the age of 40 to 45.
Rarely, a woman's ovaries stop working at a very early age, ranging anywhere from the age of puberty to age 40, and this is known as premature ovarian failure (POF). POF is not considered to be due to the normal effects of aging. Some known causes of premature ovarian failure include autoimmune disorders, thyroid disease, diabetes mellitus, chemotherapy, and radiotherapy. However, in the majority of spontaneous cases of premature ovarian failure, the cause is unknown.
Premature ovarian failure is diagnosed or confirmed by measuring the levels of follicle stimulating hormone (FSH) and luteinizing hormone (LH); the levels of these hormones will be abnormally high if menopause has occurred.
Rates of premature menopause have been found to be significantly higher in fraternal and identical twins; approximately 5% of twins reach menopause before the age of 40. The reasons for this are not completely understood. Transplants of ovarian tissue between identical twins have been successful in restoring fertility. On average, women who smoke cigarettes experience menopause significantly earlier than non-smokers.