Menopause occurs when there are very few eggs left to be fertilized, and the output of estrogen and progesterone is so small that the eggs are not stimulated to ovulate for most women, this happens in their early 50s.

For other women, some external event brings on menopause: Bilateral oophorectomy puts the body into menopause immediately because there ar no ovaries to produce estrogen and progesterone. A partial oophorectomy has a less severe impact on the body because only one ovary is removed.

Removal of the uterus speed up menopause by approximately 2-3 years.

Chemotherapy for cancer or pelvic radiation may damage the ovaries so they can no longer produce hormones. However, some younger women who are treated for cancer may begin to menstruate and ovulate again.