Illustration of fractures in osteoporotic bone tissue. Osteoporosis (brittle bone disease) causes a reduction in overall bone mass and an increase in the bone's porosity, making it more brittle and likely to fracture. It commonly affects the elderly and post-menopausal women, who experience a decrease in levels of the hormone oestrogen. It may also develop following injury or infection. Oestrogen replacements and drugs that slow the rate of bone loss are used to treat the disease. A diet rich in calcium can help make bones stronger and more resistant to osteoporosis.