Early or premature menopause is defined as menopause before the age of 40. Premature ovarian failure, surgery, and chemotherapy may all result in early menopause. About one in a hundred women may experience early menopause; some may be teenagers or in their twenties. Symptoms of early menopause tend to be very similar to those of normal menopause. Changes in the timing and duration of menstrual periods and hot flashes are common.

In some women, early menopause may be due to failure of the ovaries and is called premature ovarian failure. It is thought that such failure is due to hormonal, autoimmune or genetic processes, which result in a depletion in the number of viable eggs in a womans ovaries. This depletion may be complete, or, in approximately ten percent of women who have premature ovarian failure, partial. These women have a reduced but possible chance of becoming pregnant. Recent research has shown that female twins may be up to four times more times more likely than other women to undergo spontaneous early menopause. Either or both twins may be affected.

Surgery is another cause of early menopause. When the ovaries are removed or damaged during surgery, there is a rapid reduction in estrogen and progesterone levels and the immediate onset of menopause. Because the hormonal changes are so abrupt, menopausal symptoms tend to be more intense.

Women who undergo chemotherapy for cancer treatment may have premature menopause. Cancer-killing drugs may damage other tissues too, including ovarian tissue. Tamoxifen, a drug prescribed in certain types of breast cancer, has an anti-estrogen effect and can also trigger early menopause. Sometimes, chemotherapy-induced menopause may be temporary.

Early menopause can be extremely distressing, particularly when it occurs in younger women who may not yet have had children or completed their families. Besides treatment of menopause symptoms, some women benefit from counseling to address emotional issues.