Osteoporosis is a disease in which low bone mass leads to an increased chance of developing fractures. It is an end-stage condition, caused by a chronic disruption of skeletal homeostasis. When faced with a severe dietary shortage of calcium, the body pulls this mineral from the bones to maintain levels needed in the blood. This causes loss of bone density and strength. Bones fracture more easily; an advanced osteoporotic fracture can happen when the person is sitting down.
The consequences of osteoporosis can cause pain, loss of activity and restricted movement. However, the bone loss that precedes the osteoporotic fracture is a symptomless process, so osteoporosis may go undetected until bones become so brittle that even the slightest trauma causes a fracture, with fractures of the hip, wrist and spine being the most common. The spine is the most common region of fracture, with one third of women 65 years and older having sustained spinal vertebrae fractures, leading to loss of height, kyphosis (dowager's hump), and chronic back pain. By extreme old age, one of every three women and one of every six men will have a hip fracture which, by any measure, is the most devastating of all osteoporotic fractures.
Significant contributors to this degenerative process include nutritional, endocrine, physical, lifestyle, genetic and environmental factors. Some of the risk factors include: inadequate nutritional intake, lack of physical activity, smoking, excessive alcohol consumption and prolonged use of corticosteroids. The current medical treatment mainstay, hormone replacement therapy, slows bone loss and reduces fracture incidence, but must be taken for ten or more years to realize this benefit. Unfortunately, this approach subjects women to a long-term therapy that poses significant concern due to increased risk of breast cancer, uterine cancer and side effects.
Osteoporosis is the most common metabolic bone disease. It is most common in postmenopausal women, but can affect both men and women of any age. In 1991 it was estimated that osteoporosis affected over 20-25 million Americans and is projected to cost $30-40 billion dollars annually by the turn of the century.
The following statistics were provided in 1998 for the UK: 1 in 3 women and 1 in 12 men over 50 are affected by osteoporosis. There are over 200,000 fractures each year: a broken bone every 3 minutes. More women die after hip fractures than from cancer of the ovaries, cervix and uterus. Osteoporosis costs £3,940 billion a year. Osteoporosis is increasing by 10% a year.
Women have a four-times greater risk of developing osteoporosis than men, with post-menopausal women at greatest risk. As levels of oestrogen fall after the menopause, the bone becomes porous and fragile, and the body's bone mass diminishes. Low oestrogen levels and increase in levels of circulating cortico-steroids are also responsible for loss of bone density in anorexics and and those who are overfit and underweight (e.g. athletes and dancers). This is particularly marked in young women, who can lose up to 15% of their bone density annually, whereas post-menopausal women tend only to lose 1 to 2% a year. Even after they were again eating well enough for their periods to have restarted, bone mass was only regained very slowly.