X-ray (blue tint) of the lumbar spine of a woman suffering from osteoporosis, showing vertebral collapse. Osteoporosis is a reduction in the mass of bone causing an increase in brittleness and a greater risk of fractures, particularly of the vertebrae, hip or arm. The condition arises through an imbalance between formation & resorption of bone, most commonly occurring with increasing age. The incidence is greater in women than in men and is attributed to a decline in hormone production following the menopause. Oestrogens (sex hormones) may be used to prevent & treat age-related disease, although their use is controversial.