Osteoporosis is a decrease in bone mass and strength causing increased susceptibility to fractures.
It is the major cause of bone fractures in older people, especially postmenopausal women. Osteoporosis has no clear beginning, and until recently its first visible sign was a fracture of the hip, wrist or vertebrae. During the mid-30s, everyone begins to lose very small amounts of bone. A variety of medical and lifestyle factors may increase bone loss, causing osteoporosis to occur at a younger age. Menopause is the most predictable medical cause of osteoporosis in women due to a decrease in estrogen levels.