Condition in which bone breaks down more rapidly than it is produced; in contrast with osteomalacia, calcification of the bone is normal. The various structures in the bone are thinner, and therefore weaker, and fractures easily occur; vertebrae can collapse, causing lack of height, kyphosis and backache. Osteoporosis has many causes, the commonest of which is lack of load on the bone, for example in patients bedridden for a long time or older people with restricted movement. The condition is encouraged in older women by decreased female sex hormone production after the menopause. Osteoporosis is one of the most important causes of hip fractures in older people. In modern times weightlessness can cause deficient bone loading: astronauts who spend long periods in space find that osteoporosis can be a problem. The condition is also associated with certain disorders such as osteogenesis imperfecta, and excessive thyroid hormone and corticosteroid levels; the latter are used in the treatment of various illnesses, but can also be produced in excess by the body (Cushing’s syndrome). Treatment of osteoporosis can consist of increased activity, such as exercises for the elderly; avoiding long-term confinement to bed; a diet high in vitamins D and C, calcium, phosphate and protein; and the administration of sex hormones or anabolic steroids. The latter are hormonal preparations that encourage tissue (and thus also bone) formation. Certain resultant bone conditions, such as collapsed vertebrae, cannot be cured; painkillers may be prescribed.