Osteoporosis is an increasing problem in developed countries. This article looks at what osteoporosis is, who gets it, and risk factors for the condition.
What is Osteoporosis?
Osteoporosis is a condition in which the density of minerals in the bones (particularly calcium) is reduced. This weakens the bones and makes them more susceptible to fractures, often following relatively minor accidents. The bones most often fractured in osteoporosis are the vertebrae of the spine, the forearm and wrist, and the hip.
Although the bones may seem like rigid, unchanging structures, the minerals that give them their strength are constantly being absorbed and replaced by specialized cells in a process called “bone remodelling”. This cycle of repair and renewal keeps the bones healthy, and maintains the correct levels of calcium in the blood.
Normally, the amount of old calcium removed during bone remodelling is equal to the amount of new calcium deposited. If the balance tips, so that more is removed than is replaced, the overall mineral content of the bone decreases and osteoporosis is the result.
Causes of Osteoporosis, Risk Factors
There are three types of osteoporosis.
- Idiopathic or primary osteoporosis arises without any triggering illness. It is most common in post-menopausal women, due to loss of the female sex hormone oestrogen, which helps regulate bone remodelling. Primary osteoporosis is also occasionally seen in younger women and men, and even in children; in these cases, the cause of bone mineral loss is unclear.
- Secondary osteoporosis may occur in people with another condition that can alter bone metabolism; examples include hyperthyroidism, parathyroid disease, Crohn’s disease, rheumatoid arthritis, alcohol abuse and anorexia nervosa.
- Localized osteoporosis may develop in an arm or leg that has been immobilized in a plaster cast or due to paraplegia. Transient localized osteoporosis can occur in the spine or hip in pregnant women, but is very rare.
Risk factors for osteoporosis include:
- having close relatives with osteoporosis
- poor dietary intake of calcium during childhood and adolescence
- early menopause
- taking certain medications (e.g. steroids, anti-epilepsy drugs, some cancer treatments)
- low activity level
- tobacco smoking.
These factors either directly reduce bone density (e.g. low calcium intake) or predispose to bone loss in later life.
Osteoporosis Epidemiology
The prevalence of osteoporosis is rising in developed countries, partly due to the growing proportion of elderly people in the population and partly because of increasingly sedentary lifestyles. In the UK, it is estimated that almost three million people have osteoporosis, with over 200,000 fractures due to osteoporosis every year. In the USA, osteoporosis occurs in up to 30% of post-menopausal women. Osteoporotic fractures have a high social and economic cost, but can be reduced by prompt diagnosis and/or screening, appropriate treatments and preventive measures.
References:
Eastell R. Osteoporosis. Medicine 2005; 33(12): 61−6.
Key Facts and Figures. Accessed 09-12-10
Ralston SH. Structure and Metabolism of Bone. Medicine 2005; 33(12): 58−60.
Tobias JH. Metabolic Bone Disease. In: Axford J, ed. Medicine. Oxford: Blackwell Science, 1996.
Who is at Risk of Osteoporosis and Broken Bones? Accessed 09-12-10
Disclaimer:
The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
Join the Conversation