Cessation of menstrual periods. The woman runs out of eggs. Estrogen production drops dramatically. Menopause frequently is preceded by a few years of perimenopause.
Menstrual cycles are frequently shorter.
Menstrual cycles are often irregular. Many women will begin having hot flashes. Osteoporosis is proven to be associated with estrogen deficiency. The answer to this question is complicated. Estrogen treatment decreases the risk of dying from breast cancer.