A condition of increased bone fragility and susceptibility to bone fracture due to a loss of bone mineral density (BMD). The three main mechanisms are development of insufficient mass and strength during skeleton growth (inadequate “peak bone mass”), excessive bone depletion (resorption) and inadequate formation of new bone during “remodelling”, leading to fragile (porous) bone tissue.

Many factors increase the risk of developing osteoporosis, including being female, thin, inactive, at advanced age, and having a family history of osteoporosis. Osteoporosis is most common in women after menopause (postmenopausal osteoporosis), but may also develop in men, and may occur in anyone in the presence of particular hormonal disorders and other chronic diseases or as a result of medications.