Osteoporosis

 

What is osteoporosis?

Bone is made up of two main components. The first is a protein substance that forms the basis of the skeleton. The second component consists of calcium salts which are deposited within the protein and which give it its hardness and add to its strength. With age, the loss of both of these components from the bones occurs in every individual, leading to some thinning of the bones. Osteoporosis is a condition in which this thinning of the bones occurs to an unusually high degree and in which the individual is at risk from fractures, especially of the hips, wrists and vertebrae (the bones of the spine). It is a condition which mainly occurs in women over the age of 50, although younger women and some men can also suffer from the condition.

How common is it?

Osteoporosis is very common, affecting one in three women and one in twelve men over the age of 50. Younger people are also sometimes osteoporotic. It is responsible for about 40,000 vertebral fractures (fractures of the bones of the spine) and about 70,000 hip fractures in the UK. The result of this is that more than a third of women and a quarter of men will sustain one or more fractures attributable to osteoporosis at some time in their life.

 

Why does it occur?

Doctors do not yet know everything they would like about the causes of osteoporosis, but in recent years much research about the condition has been done, so more is known about it than ever before. Most people reach their maximum bone strength at about the age of 35. After this age all men and pre-menopausal women (those who have not yet had their menopause) lose bone thickness quite slowly at a rate of about one per cent a year.

Women lose bone thickness more quickly than this after the menopause. This occurs whether the menopause is at the usual age of approximately 50 years, or as a result of premature menopause or removal of the ovaries during surgery. The female hormone oestrogen protects against rapid loss of bone, so when oestrogen levels fall after the menopause, this protection is lost. This faster rate of post-menopausal bone loss is the most common cause of osteoporosis. However, there are certain drugs and medical conditions and various factors in a person's lifestyle that may also speed up bone loss. These will be discussed below. Similarly, one cause of osteoporosis in men is lack of the male hormone testosterone, which also seems to give some sort of protection against loss of bone thickness in men.

 

Who is more at risk of developing osteoporosis?

Certain groups of people are at more risk of developing osteoporosis. Some of the factors listed are beyond the control of the individual person but some are not, and therefore it is often possible for someone to lower their chances of getting the condition. Those at higher risk include:

  • post-menopausal women, especially those with premature (early) menopause occurring either naturally, or due to having both ovaries removed (oophorectomy) as a result of surgery or radiotherapy
  • people who have to take steroids over a long period of time for another medical condition such as severe asthma or certain types of arthritis
  • thin people, including especially those with anorexia nervosa (sometimes also called 'slimmers disease')
  • people with a family history of osteoporosis in close relatives
  • people with reduced mobility
  • smokers
  • people who have a diet which is low in calcium
  • people who have poor nutrition and/or low levels of activity in childhood and early life
  • those with a high intake of alcohol
  • men who have a medical condition which results in low levels of the male hormone testosterone
  • those with certain other medical conditions which affect the absorption of food from the gut such as cystic fibrosis or a disease called coeliac disease
 

What symptoms does osteoporosis cause?

Osteoporosis may not cause any symptoms at all until it is bad enough to cause pain due to distortion or breakage of the bones. The most commonly affected bones are in the vertebrae (bones of the spine) and the bones of the wrists and hips, although anywhere in the body can be affected. Therefore, the first sign of a problem may be that a person notices that they are developing a curvature of the spine, causing them to have a permanent stoop. This spinal curvature occurs, as a result of a slow compression of the weakened vertebrae, which makes them become wedge-shaped. This can eventually cause quite a pronounced forward curve of the spine called a 'kyphosis'. Alternatively, someone with osteoporosis will notice that even quite minor falls result in a fracture of the hip or wrist.

 

How is osteoporosis diagnosed?

A doctor may strongly suspect that osteoporosis is present from a history of frequent fractures in a patient or from the development of the classic kyphosis mentioned above. However, the only accurate test for osteoporosis is bone densitometry, usually carried out by means of a DEXA (dual x-ray absorptiometry) scan. This is a painless investigation that scans the hips and part of the spine.

A DEXA scan measures the amount of calcium in the bone and therefore provides a measurement of bone mass. Access to this type of scan varies throughout the country but they are becoming more readily available.

Other methods of measuring bone density exist, such as special ultrasound measurements of the heel bone of the foot. However, these are currently thought not to be as accurate as DEXA scanning although they can be useful to provide a general screening test.

Sometimes doctors will organise blood tests to exclude other conditions and also to look for possible contributory causes for the osteoporosis. For instance, some thyroid problems and low levels of female or male hormones can help to cause osteoporosis. Knowing this will influence how the condition is treated.

 

What is the treatment for osteoporosis?

A number of treatments exist to slow the rate of bone thinning in people who have osteoporosis, but unfortunately as yet there is still no treatment which restores osteoporotic bone to normal. It is therefore important to try to prevent bone loss from happening in the first place if at all possible, so various preventative measures are discussed below. Drug treatments for the condition fall into four main groups, which are outlined below.

Hormone replacement therapy (HRT)

HRT used to be the treatment of choice for the prevention of osteoporosis in postmenopausal women. However, two large research studies in 2002 and 2003 found that HRT increased a woman's chances of developing breast cancer, endometrial (womb) cancer and cancer of the ovary as well as an increased risk of heart attacks and thrombosis (blood clots in the legs and lungs).

As a result, for most women, the risks of HRT for the treatment of osteoporosis outweigh the benefits and it is now only recommended for those women who are unable to take other osteoporosis treatments, or who do not respond to them, and are at significant risk from their osteoporosis. In these cases, the doctor or specialist will discuss the risks and benefits of HRT with the individual woman concerned.

HRT may still be recommended for women under the age of 50 who have suffered a premature menopause since it may still have a place in the simultaneous treatment of their menopausal symptoms (hot flushes, night sweats etc.) and the prevention of the onset of osteoporosis.

Raloxifene

This is a relatively new drug that has been developed which has similar properties to HRT in the treatment and prevention of osteoporosis but it is not actually a hormone and therefore does not cause an increase in the risk of breast cancer.

Bisphosphonates

These are drugs that have been found to reduce the activity of the cells in the body, called osteoclasts, which destroy bone. Therefore bisphosphonates help to prevent further bone loss in women or men in whom osteoporosis has actually been diagnosed. The first of these drugs to be produced was one called etidronate, which is given with calcium in a preparation called Didronel PMO. This has been found to reduce further bone loss and can safely be used for several years' continuous therapy. Another drug with similar properties is alendronate (Fosamax) which now comes in a once weekly tablet. A newer bisphosphonate called risedronate (Actonel) is now also licensed for the treatment of osteoporosis.

Calcium and vitamin D

Between one and one and a half grams of calcium is required in the diet daily to ensure good bone health in osteoporosis. Most osteoporotic patients do not consume this much, so calcium supplements are often recommended, together with vitamin D. This helps the skeleton to absorb calcium since many elderly patients are also slightly deficient in this vitamin. Some preparations now exist which combine calcium and vitamin D. Calcium and vitamin D is sometimes recommended to be taken in addition to the bisphosphonates.

Calcitonin

This is a natural substance that is present in the body and helps to control calcium levels in the bloodstream. However, injections of calcitonin are sometimes given to treat osteoporosis usually in combination with calcium and vitamin D supplements.

 

Can osteoporosis be avoided?

In some cases osteoporosis is difficult to avoid, for example, when it is caused by long-term steroid therapy. However, in many instances the individual can do several things to lessen their chances of developing the condition. There is evidence that both weight-bearing exercise and increased calcium in the diet are of benefit in strengthening bones. A litre of milk contains one gram of calcium so a modest intake of dairy products would meet the recommended daily requirement. Even an extra glass of milk per day has been found to significantly increase bone density.

Adequate vitamin D intake helps the absorption of calcium from the diet and its incorporation into the bones. Exposure to sunlight helps to boost the body's vitamin D levels. However, in these days of awareness of the dangers of too much sunlight on the skin, there is more reliance on the diet to provide vitamin D. An intake of 600 to 800 IU (international units) of vitamin D a day is recommended.

Alcohol in moderation (one to two units per day) has a slightly protective effect, but taken in excess may hasten bone loss. Also, a lot of salt in food has been found to reduce calcium absorption from the gut and should therefore be avoided, as should an excess of protein. Smoking is a risk factor for osteoporosis and so is not advisable, especially in those at high risk of osteoporosis.

Finally, those who think they may be at special risk of developing osteoporosis should discuss the possibility of having their bone density measured so that their risk can be assessed and any necessary measures undertaken to prevent or slow down the disease.

 

Where can I get further information?

Apart from contacting your GP, the following organisations may be of further help:

National Osteoporosis Society
Camerton
Bath
BA2 0PJ
Telephone: 01761 471771
Helpline: 0845 4500230
Website:www.nos.org.uk