Osteoporosis is a bone disorder caused by loss of bone mass, resulting in abnormal bone structure and an increased risk of fracture.

What is osteoporosis?

Computer artwork of a human female skeleton degenerating due to osteoporosis. At left is a normal skeleton. The degeneration, seen from left to right over time, is the loss of height and the backwards curvature of the spine.

Computer artwork of a human female skeleton degenerating due to osteoporosis. At left is a normal skeleton. The degeneration, seen from left to right over time, is the loss of height and the backwards curvature of the spine.

Osteoporosis is a reduction in the amount of bone in the skeleton, which reduces the strength of bones and makes them more likely to break (fracture). The commonest fractures in osteoporosis are spine, hip and wrist fractures. Osteoporosis is the commonest acquired bone disorder and cause of fractures in adults. One in two women and one in five men over the age of 50 will have a fracture due to osteoporosis.

What causes osteoporosis?

Bone is a living tissue that is constantly being renewed through a process known as remodelling. Cells in the bone called osteoclasts break down old damaged bone to make way for new bone that is laid down by cells called osteoblasts. In normal healthy bones, about 10% of the bone is replaced in this way every year, and the amount of bone removed is balanced by the amount of new bone laid down. With older age, and after the menopause in women, the remodelling process goes too quickly, and becomes unbalanced so that more bone is broken down than can be replaced.

Most osteoporosis has no specific cause (primary osteoporosis) but there are a number of reasons why some people are more likely to have osteoporosis than others.

Oestrogen deficiency, normally as a result of the menopause, is the commonest cause of osteoporosis, although some diseases can also result in osteoporosis. These can include various endocrine disorders such as:

Other secondary causes include:

  • inflammatory arthritis
  • inflammatory bowel disease
  • coeliac disease
  • chronic kidney disease.

Some medications can cause osteoporosis:

  • steroids (like prednisolone)
  • some anti-epileptic drugs
  • anti-oestrogen treatment for breast cancer (such as aromatase inhibitors)
  • anti-testosterone treatment for prostate cancer.

There are also lifestyle factors that can affect the risk of developing osteoporosis. For example, smoking, drinking excessive alcohol and not exercising increase the risk of developing osteoporosis, as does being underweight. Regular exercise and a healthy diet that includes an adequate amount of calcium (two to three portions of dairy food per day) are ways of reducing the risk of developing osteoporosis. Vitamin D is important for bone strength – it is manufactured by the skin when exposed to sunlight, and is present in just a few foods (like oily fish) but many people in the UK have vitamin D deficiency. In 2016 the UK government recommended that most people should take a vitamin D supplement in the winter, and some people should take it all year round.

What are the signs and symptoms of osteoporosis?

Osteoporosis has no symptoms (asymptomatic) until fractures occur. Any fracture that occurs following minor injury should raise suspicion of underlying osteoporosis. The most common fractures that occur in osteoporosis are those of the hip, wrist and spine bones (vertebrae), although fractures can occur at any site. Usually, fractures of the hip and wrist occur after a fall, but fractures of the vertebrae may occur without any obvious injury. Such fractures may not cause any symptoms or are accompanied by the development of acute back pain, which may disappear over weeks or months. Multiple fractures of the spine can cause loss of height and significant spinal deformities and patients may develop marked abnormal curvature of the spine (kyphoscoliosis).

How common is osteoporosis?

About half of women and one in five men over the age of 50 will have a fracture from osteoporosis at some point in their lifetime. Vertebral and hip fractures are the most commonly encountered. However, although the chances of having a hip fracture increase as age advances, only about 0.3–0.5% of women over the age of 75 will suffer from a hip fracture. This increases to about 1% of women over the age of 85. More women than men tend to have fractures of the hip.

Is osteoporosis inherited?

There is a tendency for osteoporosis to run in families, but the inheritance of a specific gene or genes has not yet been identified. This means individuals may inherit a greater likelihood of developing osteoporosis, but if one of the parents is affected, it does not necessarily mean that the children will develop the condition. 

How is osteoporosis diagnosed?

Diagnosis of osteoporosis is usually made by measuring bone density with dual energy X-ray absorpimetry (DEXA scanning) and, routinely, this will be done on the hips and vertebrae. In severe osteoporosis, bones may appear thin even on simple X-rays and these may also show fractures in vertebrae.  

Blood tests may also be carried out to check for other causes of osteoporosis and these include measurement of calcium profile, thyroid function and parathyroid hormone.

How is osteoporosis treated?

The major class of drugs used to treat osteoporosis is bisphosphonates. These drugs stick to the surface of bones, where they can enter bone cells and prevent the cells breaking down bone, so preventing bone loss and keeping remodelling in balance. They have been shown to reduce the risk of hip and vertebral fractures. The most commonly used bisphosphonates are risedronate and alendronate, which are normally taken once weekly. Zoledronic acid may also be used and is given as a once-yearly infusion. Vitamin D and calcium should be replaced in all patients starting treatment for osteoporosis to make the treatment as effective as possible.

Oestrogens (such as those found in hormone replacement therapy) can also be given to treat postmenopausal osteoporosis, although long-term use is no longer recommended and it is usually only prescribed for treating osteoporosis in women who also have menopausal symptoms. 

In patients who cannot take bisphosphonates, or thos who do not show a good response, some other treatments are available, including denosumab (injected every six months), teriparatide (injected every day for two years), raloxifene and strontium ranelate (taken by mouth).

Are there any side-effects to the treatment?

The side-effects of taking bisphosphonates, if any, are usually mild and can include indigestion, a change in bowel habits (constipation or diarrhoea), tiredness, feeling sick and mild flu-like symptoms.     

In patients treated with bisphosphonates for a longer time, there are other possible side effects (osteonecrosis of the jaw and atypical femoral fracture), but these are very rare. If you are having treatment with bisphosphonates and you get hip, thigh or groin pain, you should see your doctor because you may need an X-ray to check for fractures.

What are the longer-term implications of osteoporosis?

The long-term implications of osteoporosis are the increased risk of fractures from minor injury. Immobility caused through these fractures can also have long-term consequences because it reduces physical ability, particularly in the elderly. Exercise is important in building bones, making it important for all patients with osteoporosis to have regular exercise, particularly weight bearing and resistance exercise. Patients should also try to maintain a healthy lifestyle and diet. Alcohol and smoking are also risk factors for osteoporosis and their use should be discouraged.     

Last reviewed: Mar 2017