Osteoporosis. Computer artwork depicting a human pelvis, rib cage and skull to illustrate osteoporosis. Osteoporosis is a condition where loss of bone calcium causes a reduction in the bone density. It is most common in women after the menopause because they no longer produce the hormone oestrogen that helps to retain bone mass. Consequently the bone becomes brittle and liable to fracture easily under trauma, for example a fall. A diet rich in calcium and vitamin C, and regular weight-bearing exercise can help to prevent the onset of osteoporosis.