Osteoporosis is the gradual reduction in bone density due to the loss of essential bone minerals, such as calcium. From the age of 35 onward bones slowly begin losing calcium in both men and women, but with the onset of menopause the loss of calcium is far greater in women. Some of this can be attributed to hormonal changes, as reductions in oestrogen contribute to the loss of calcium. When this occurs, bones become frail and the risk of fracture is increased particularly in the spine, hip and wrist.