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.

Osteoporosis is a reduction in the amount of bone in the skeleton, making it less dense. This decreases the strength of the bones and makes them more likely to break (fracture) when they normally wouldn’t. The type of fractures caused by osteoporosis are known as osteoporotic fractures and they most commonly happen in the spine, hips and wrists.

Osteoporosis is the commonest acquired bone disorder and an important cause of fractures in adults. One in two women and one in five men over the age of 50 will have a fracture at least once in their lifetime due to osteoporosis.

What causes osteoporosis? 

Bone is a living tissue that is constantly breaking down and rebuilding its structure through a lifelong process known as remodelling. Special cells within the bone, called osteoclasts, break down old, damaged bone to make way for new, healthy and strong bone that is laid down by another type of cells called osteoblasts. Remodelling is an important process because it keeps bones healthy and repairs minor damage, which prevents fractures. It is a continuous, lifelong process that helps maintain bone strength and shape.

Approximately 10% of the normal 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 happens at a faster rate and becomes unbalanced so that more bone is broken down than can be replaced. 

Osteoporosis is more common in women and older people, however men and younger people can also be affected. Most of the time, there is no specific cause behind osteoporosis (primary osteoporosis) although, in some occasions, there might be reasons behind it (secondary osteoporosis). Some conditions and medications that can increase the risk of osteoporosis are:
1. Hormone abnormalities.

• Oestrogen deficiency in women. This is usually the result of menopause in women, although there are other conditions in younger women that can also lower oestrogen levels. This is one of the reasons why osteoporosis is more frequent in women.
• Overactive thyroid (hyperthyroidism) 
• High levels of parathyroid hormone (the commonest cause being primary hyperparathyroidism)
• Excess cortisol production (Cushing’s syndrome)
• Low levels of testosterone in men (hypogonadism)

2. Other causes include:

• Inflammatory arthritis (especially rheumatoid arthritis)
• Inflammatory bowel disease
• Coeliac disease 
• Chronic kidney disease

3. Medications such as:

• Steroids (like prednisolone or anabolic steroids)
• Some anti-epileptic drugs
• Anti-oestrogen treatment for breast cancer (such as aromatase inhibitors)
• Testosterone-lowering treatments for prostate cancer.

Some lifestyle factors can also affect the risk of developing osteoporosis. For example, smoking, drinking excessive alcohol and not exercising can increase the risk of developing osteoporosis, as does being underweight.

Regular exercise and a healthy diet are ways of reducing the risk of developing osteoporosis. Calcium makes bones strong and most adults need approximately 700mg of calcium a day; this can be achieved by eating low fat dairy food every day (two to three portions) or by adding bread and cereals, certain fish (sardines, pilchards, crab and salmon for example) and vegetables (broccoli and oranges) to the diet. There are some dairy free alternatives enriched with calcium that people unable to eat diary can incorporate in their diets too. Vitamin D is also important for bone strength – it is manufactured by the skin when exposed to sunlight and this provides approximately 90% of our vitamin D. The remaining 10% of vitamin D is obtained from the diet. Many people in UK have Vitamin D deficiency, especially in the winter, due to the limited sun exposure. 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 seen 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 happen without any obvious injury. Such fractures may not cause any symptoms or may be accompanied by the development of acute back pain, that may disappear over weeks or months. Multiple fractures of the spine can cause loss of height and significant spinal deformities, including a marked abnormal curvature of the spine (kyphoscoliosis). 

How common is osteoporosis? 

In England and Wales, about 2 million women are thought to have osteoporosis. Osteoporosis affects more women than men because women lose bone material faster than men, especially as their oestrogen levels fall following menopause. 1 in 50 women will have osteoporosis at the age of 50, which increases rapidly to 1 in 2 by the age of 80. About 1 in 3 women and 1 in 5 men in the UK will have a fracture from osteoporosis at some point in their lifetime.

Fractures are the commonest and usually the first sign of osteoporosis. Simple falls (from the height of a standard chair or even less) are enough to fracture a bone if you have osteoporosis.

Vertebral and hip fractures are the most commonly encountered. 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. Although an individual is more likely than the general population to have osteoporosis if one of their parents is affected, this is not always the case. 

How is osteoporosis diagnosed? 

Diagnosis of osteoporosis is usually made by measuring bone density with a scan knows as dual energy X-ray absorptiometry scan (DEXA scan). DEXA scans are routinely done on the hips and vertebrae (back bones) although the wrists can also be scanned. In severe osteoporosis, thin bones or vertebral fractures may be seen on simple X-rays. 

Blood tests may also be carried out to check for other causes of osteoporosis and these may include measurement of calcium, Vitamin D, testosterone (in men), Vitamin D and parathyroid hormone levels. 

How is osteoporosis treated? 

Exercise is important in building bones; hence it is advised that patients with osteoporosis have regular exercise, particularly weight bearing and resistance exercise.

Patients should also try to maintain a healthy lifestyle and a diet rich in calcium. If calcium intake cannot be adequate, calcium supplements might be required. Online tools exist can help with assessing dietary calcium intake (https://www.osteoporosis.foundation/educational-hub/topic/calcium-calculator).

Alcohol and smoking are also risk factors for osteoporosis and their use is discouraged. The most commonly used drug to treat osteoporosis is a bisphosphonates. Bisphosphonates stick to the surface of bones where they can enter bone cells and prevent the osteoclasts from breaking bone down, hence preventing bone loss and keeping the remodelling process 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 orally (by mouth) once weekly. Zoledronic acid may also be used and is given as a once-yearly infusion (drip through a vein).

Calcium and Vitamin D are essential to make bone and should be replaced when low in all patients starting treatment for osteoporosis. Elderly people that are housebound should also have vitamjn D supplementation. Although studies have shown that vitamin D does not prevent falls or fractures, and does not improve bone density significantly, vitamin D and calcium are essential in patients starting treatment for osteoporosis because they make the treatment as effective as possible.

Oestrogens (i.e. hormone replacement therapy, HRT) can also be given to treat postmenopausal osteoporosis. However, as they can be associated with side effects, it is important that women discuss the potential risks of HRT with their doctor before starting HRT. Oestrogens are particularly useful in preventing osteoporosis in women who develop premature menopause (before the age of 40 years).

Some alternative treatments are available for those patients who cannot take bisphosphonates, or for those who do not show a good response to them. These available medications include denosumab (injected every six months), teriparatide (injected every day for two years) and raloxifene (taken by mouth).  

Are there any side-effects to the treatment? 

The side-effects of taking bisphosphonates can include indigestion, a change in bowel habit (constipation or diarrhoea), tiredness, dizziness or headaches, aches and pains, swelling of the legs, feeling sick and flu-like symptoms.

Patients treated with bisphosphonates for a longer time can rarely get other side effects, such as osteonecrosis of the jaw and atypical (not typical) femoral fractures. Hence, it is important to have a dental check-up (and any required dental procedures) before or as soon as possible after starting treatment with bisphosphonates. 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 atypical fractures. 
 

What are the longer-term implications of osteoporosis? 

The long-term implications of osteoporosis are the increased risk of fractures from minor injury. These can cause significant pain and severe disability, often causing reduced quality of life and immobility, particularly in the elderly. Fractures can also be associated with decreased life expectancy. For instance, hip fractures always require hospitalisation and can be life threatening in 1 in 5 cases.

Osteoporotic fractures are very distressing to the individual, but also add to healthcare costs as they cost the NHS over £1.73 billion every year.

Maintaining a healthy lifestyle and diet, undertaking regular exercise, and minimising alcohol and smoking exposure are the most important steps to preventing osteoporosis.