the post-menopause phase of life begins at menopause, which is 1 year after your last menstrual period. post-menopause usually begins around age 50. but it could happen anytime from your mid-40s to your later 50s.
after menopause, your estrogen settles at a low level. low estrogen helps reduce the risk of various types of cancer. but it also leads to bone thinning. this sometimes can cause osteoporosis. a variety of treatments are available if you have symptoms after menopause.
menopause can begin early and suddenly after removal of the ovaries or after cancer treatment that damages the ovaries.