Postmenopausal osteoporosis describes osteoporosis that occurs in women after menopause. It is the most common type of osteoporosis.
Other causes of osteoporosis include immobilization, prolonged use of medications (prednisone), kidney disease or hormonal disorders (hypothyroidism).
Menopause is the time in a woman's life, usually after age 45, when her menstrual period stops. Menopause happens because the woman's ovaries stop producing the hormones estrogen and progesterone.
Estrogen levels are closely associated with bone health. Estrogen helps women absorb calcium, which is important for building strong bones. After menopause, many women begin losing bone faster than they can build new bone. Osteoporosis develops when bone removal (a process called bone resorption) occurs too quickly or when bone addition (called bone replacement) occurs too slowly.
For women, bone loss is fastest in the first few years after menopause, and it continues into the postmenopausal years. Postmenopausal osteoporosis is more likely to develop in women who did not reach optimal peak bone mass during their bone-building years (adolescence).
Reference: The National Institute of Arthritis and Musculoskeletal and Skin Diseases