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Osteoporosis is a progressive, systemic skeletal disorder charcaterised by loss of bone tissue and disruption of bone micro architecture which leads to bone fragility and a consequent increased risk of fracture (1).
- bone formation exceeds bone resorption in youth, but by the third decade of life there is a gradual loss of bone mass. Hence osteoporosis is usually an age-related disease.
- in contrast to osteomalacia, the bone mineralization process is normal
It is the most common bone disease affecting the human (2)
- prevalence increases with age, it can affect both sexes, but women (especially post-menopausal women) are at greater risk because the decrease in oestrogen production after the menopause accelerates bone loss to a variable degree
- it is estimated that annually there are 180,000 osteoporosis-related symptomatic fractures in England and Wales. Of these, 70,000 are hip fractures, 25,000 are clinical vertebral fractures, and 41,000 are wrist fractures
The World Health Organization (WHO) has established diagnostic criteria for osteoporosis based on the measurement of bone mineral density (BMD), expressed as the T-score, which is the number of SD below the mean BMD of young adults at their peak bone mass:
- normal BMD: T-score of -1 SD or above
- osteopenia: T-score of between -1 and -2.5 SD
- osteoporosis: T-score of -2.5 SD or below
- established (severe) osteoporosis: T-score of -2.5 SD or below with one or more associated fractures
In addition to increasing age and low BMD, other clinical factors have been associated with increased fracture risk. Some of these clinical risk factors are at least partly independent of BMD, and include
- parental history of hip fracture
- alcohol intake of 4 or more units per day
- prior fracture
- long-term systemic use of corticosteroids
- rheumatoid arthritis
Factors that are known to be indicators of low BMD include low body mass index (defined as less than 22 kg/m2), and medical conditions such as ankylosing spondylitis, Crohn's disease, conditions that result in prolonged immobility, and untreated premature menopause
Last edited 08/2020 and last reviewed 11/2020