Osteoporosis
Introduction
Osteoporosis is a condition that affects the bones, causing them to become thin and weak.
Approximately three million people in the UK have osteoporosis, and there are over 230,000 fractures every year as a result.
Osteoporosis happens more commonly in old age, when the body becomes less able to replace worn-out bone. Special cells within the bones, called living bone cells, are no longer able to break down old bone and renew it with healthy, dense new bone.
As you get older, you also lose a certain amount of bone, causing the bones to become thinner. The bones become fragile and more likely to break (fracture), particularly the bones of the spine, wrist, and hips.
Bone is a living tissue that is constantly repairing itself. It is made of a hard outer shell, which contains a mesh of collagen (tough elastic fibres), minerals, blood vessels and bone marrow. This mesh looks a bit like a honeycomb, with spaces between the different parts. Healthy bones are very dense, and the spaces within bones are small. In bone affected by osteoporosis, the spaces are larger, making the bones weaker and less elastic.
Bones are repaired and reinforced by a range of proteins and minerals, which are absorbed from the bloodstream. They include calcium, phosphorus, proteins and amino acids. The growth and sex hormones control the amount of mineral substance deposited in the bones. Changes in hormone levels can therefore affect the strength of the bones. For example, the female hormone oestrogen offers some protection against osteoporosis. After the menopause, oestrogen levels fall, often causing the bones to thin quickly.
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Symptoms
Osteoporosis is a condition that develops slowly over several years. Symptoms are not obvious in the early stages and can take months or years to appear. Signs of osteoporosis include joint pain, difficulty standing or sitting up straight, or fracturing a bone without much force or impact.
When the bones are significantly thinned (low in bone mass), breakages of the wrist, hip, or spinal bones (vertebra) are most common. A cough or a sneeze may cause the fracture of a rib, or the partial collapse of one of the bones of the spine.
A fractured bone in an older person can be serious, because the bone is no longer able to repair itself effectively. This can lead to arthritis, and even disability; some older people are unable to live independently following an injury.
The characteristic stooping (bent forward) position that is common in older people is a visible sign of osteoporosis. It happens when the bones in the spine are fractured (cracked), making it difficult to support the weight of the body.
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Causes
The bones are thickest and strongest in early adult life. From around the age of 35, more bone cells are lost than are replaced. This causes the bone to become thinner and weaker. People who exercise when they are young, and who remain active into old age, are less likely to get osteoporosis, because bones stay strong by being used.
There are a number of other factors that can increase your risk of osteoporosis:
Women are at greater risk of osteoporosis than men. This is due to the decrease in the hormone oestrogen after the menopause, which is essential for healthy bones. Women are at greater risk of developing osteoporosis when they have:
- An early menopause (before the age of 45);
- A hysterectomy before the age of 45, especially when the ovaries are also removed;
- Absent periods for a long time (more than 6 months) as a result of over-exercising or over-dieting.
The male hormone, testosterone, also helps to keep the bones healthy. Men continue to produce this hormone into old age, but the risk of osteoporosis is increased in individuals with low levels of testosterone.
Diseases of the hormone-producing glands may cause osteoporosis. The female hormone, oestrogen, and the male hormone, testosterone, are important for keeping bones strong, by processing minerals such as calcium. Osteoporosis can be triggered by hormone diseases, including:
- Hyperthyroidism (over-active thyroid gland);
- Disorders of the adrenal glands. In Cushing’s syndrome, overproduction of cortisol (a hormone produced in the adrenal glands) causes osteoporosis;
- Reduced output of sex hormones (oestrogen and testosterone);
- Disorders of the pituitary gland; and
- Diabetes.
Other factors that can increase the risk of osteoporosis include:
- A close family history of osteoporosis;
- Long periods of inactivity, such as long-term bed rest. Bones stay strong by being used and by having physical forces applied to them. Weight bearing exercise such as walking and running stretch and contract the muscles, encouraging the bones to get stronger;
- Heavy drinking and smoking;
- Malabsorbtion problems such as Coeliac disease and Crohn's disease;
- Long-term use of high dose corticosteroid treatment (widely used for conditions such as arthritis and asthma), which can affect bone strength;
- Not enough calcium;
- Low vitamin D levels;
- Very low body mass (e.g.- being very underweight, or having thin bones as a result of eating disorders).
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Diagnosis
Osteoporosis is not often diagnosed until the weakening of the bones has led to a broken bone. An X-ray cannot reliably measure bone density but is useful to identify spinal factures.
DEXA scan
A bone density scan, called a dual energy X-ray absorptiometry (DEXA) scan, measures the density of bones and compares this to a normal range.
The difference between your bone density and this average is calculated and you are given what is called a ‘T score’. If your T score is between 0 and 1, you're considered to be within the normal range. If it is between -1 and -2.5, you will be diagnosed with osteopenia, which is the name for the category of bone density between normal and osteoporosis.
You will be classed as having osteoporosis if your T score is below -2.5.
This test helps to measure the strength of bones and the risk or fracture.
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Treatment
There are a number of different treatments available for osteoporosis:
Hormone replacement therapy (HRT)
HRT is used for women going through the menopause as it helps to maintain bone density and reduce fracture rates during the treatment. However, HRT is not always recommended as the first treatment for osteoporosis specifically, because it can slightly increase the risk of stroke, heart disease and breast cancer. You should discuss the benefits and risks of HRT with your GP.
Testosterone treatment
Testosterone treatment for men is useful in the relatively rare cases when osteoporosis is due to insufficient production of male sex hormones.
Bisphosphonates
Bisphosphonates are non-hormonal drugs that maintain bone density and reduce fracture rates. The rate at which cells called osteoclasts break down bone is slowed, and the production of new bone increases. Strontium ranelate can be used as an alternative, if bisphosphonates are found not to be suitable. Your GP will advise you of the best course of treatment.
Calcitonin
Calcitonin is a hormone made by the thyroid gland. It inhibits the cells that break down bone.
Calcium and vitamin D supplements
Calcium and vitamin D supplements can be of benefit for older people, male and female, to reduce the risk of hip fracture. Having enough calcium in your diet when you are young is important in minimising the risk, especially for women. You should aim to eat or drink 700 mg of calcium each day, which is roughly equivalent to one pint of milk (preferably semi-skimmed). If you are not getting enough calcium in your diet, ask your GP for advice about taking a calcium supplement. All people over the age of 65 should take a vitamin D supplement.
Selective Estrogen Receptor Modulators (SERMs)
SERMs are drugs have a similar effect on bone as the hormone oestrogen. They help to maintain bone density and reduce the risk of fracture, particularly at the spine.
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Complications
Osteoporosis can cause a loss of height as a result of fractures in the spinal column. This means the spine is no longer able to support your body’s weight, and it causes the characteristic hunched posture. It is common for minor falls to cause breaks or fractures to the wrist, forearm, neck, or hip bones.
Some people become disabled, as a result of weakened bones. Hip replacements are often needed following hip fractures, and this can leave people unable to walk independently. The decrease in mobility is a common reason for admitting people to nursing homes, where full-time care can be given.
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Prevention
Your genes determine the potential height and strength of your skeleton. However, lifestyle factors, such as diet and exercise, can influence how healthy your bones are and the rate at which they repair themselves. Following a healthy lifestyle throughout life is the best way to delay the onset of osteoporosis, and slow the rate at which your bones become brittle.
Regular exercise is essential. Try to do at least 30 minutes of exercise 3-4 times a week. Two types of exercise are particularly important in improving bone density and helping prevent osteoporosis - weight-bearing exercise and resistance exercise.
Weight-bearing exercises are those where your feet and legs are supporting your own weight. For younger people, high-impact weight-bearing exercises are best. Jogging, skipping, dancing, aerobics and even simply jumping up and down on the spot all provide a useful jolt to your hips and spine that helps strengthen them.
For older people, milder forms of weight-bearing exercise should be sufficient and safe, such as brisk walking, keep fit classes, climbing an average staircase 10 times a day, or a mild game of tennis. Swimming and cycling are not weight-bearing exercises.
Resistance exercises are those that use muscle strength, where the action of the tendons pulling on the bones seems to boost bone strength. Examples include press ups, weight lifting, or using weight equipment at a gym. They also include simpler exercise such as repeatedly lifting a tin of food – this can help strengthen the bones in the wrist.
Other lifestyle factors that can help prevent osteoporosis include:
- eating a diet that contains plenty of calcium - at least 700 mg per day,
- quitting smoking - cigarette smoking is associated with increased risk of osteoporosis, and
- limit your alcohol intake - the recommended daily amount is between 3-4 units for men and between 2-3 units for women.
Older people with brittle bones can do things to reduce the risk or fracturing or breaking a bone. It’s a good idea to check your home for hazards that you may trip over, such as trailing wires, and to make sure you have regular sight and hearing tests. Some older people wear special protectors over their hips to cushion any fall.
Your GP will be able to offer you help and advice about changes to your lifestyle.
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