Lee Chung Horn
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OSTEOPOROSIS 

What is Osteoporosis?

Osteoporosis literally means 'porous bones'.

The bones in our skeleton are made of a thick outer shell and a strong inner mesh filled with collagen (protein), calcium salts and other minerals. The inside looks like honeycomb, with blood vessels and bone marrow in the spaces between bone. Osteoporosis occurs when the holes between bone become bigger, making it fragile and liable to break easily. Osteoporosis usually affects the whole skeleton but it most commonly causes breaks (fractures) to bone in the wrist, spine and hip.

Bone is alive and constantly changing. Old, worn out bone is broken down by cells called osteoclasts and replaced by bone building cells, called osteoblasts. This process of renewal is called bone turnover.

In childhood the cells that make new bone work faster, enabling the skeleton to increase in density and strength. During this period of rapid bone growth it takes the skeleton just two years to completely renew itself; in adults this takes seven to ten years. Bones stop growing in length between the ages of 16-18 but continue to grow in strength into your mid-twenties. By this age your bones have reached their maximum potential strength (peak bone mass). Up until the age of 35 a balance between bone breakdown and new bone formation means that bone density stays stable. After this age, bone loss increases as part of the natural ageing process. This can lead to osteoporosis and an increased risk of fracture, particularly in women, due to accelerated bone loss at the menopause.

Who is at risk?

We are all potentially at risk of osteoporosis because of the bone loss that occurs as we get older, particularly as we are living longer as a population. There are also many other factors which can increase your risk:

Women

-- A lack of oestrogen, caused by early menopause (before the age of 45).
-- early hysterectomy (before the age of 45), especially if both ovaries are removed (oophorectomy).
-- missing periods for six months or more (excluding pregnancy) as a result of over-exercising or over-dieting.

Men

-- low levels of the male hormone, testosterone (hypogonadism).

Men and Women

-- long-term use of corticosteroid tablets (for conditions such as asthma, arthritis)

-- maternal history of a hip fracture

-- malabsorption, inflammatory bowel disease (Crohn's disease or ulcerative colitis) and gastric surgery.

-- long-term immobility

-- heavy drinking

-- smoking

-- low body weight.

Warning signs

If you have already broken a bone after a minor bump or fall, you may already have osteoporosis. Other warning signs include height loss and kyphosis (curvature of the spine). If you also have a poor diet that is low in calcium and you take little weight-bearing exercise you may also be at risk of having osteoporosis. The good news is that osteoporosis can be treated in most cases and there are many ways to help to prevent osteoporosis and keep bones healthy.

How do I know if I have osteoporosis?

Because you cannot see or feel your bones getting thinner you will probably be quite unaware of any problems with your bone health. Osteoporosis is a silent disease and for most people, the first sign that something is wrong can be when they break a bone, often in the wrist or spine, after a minor bump or fall. Osteoporosis should not be confused with osteoarthritis, commonly called 'rheumatism'. They are different things.

Wrist fractures are particularly common in women in their fifties but sadly osteoporosis frequently goes undiagnosed. In the spine, osteoporosis can cause the small vertebrae to crush or wedge, often causing chronic pain. However, some people may not experience pain, and the first indication of osteoporosis might be the resulting loss of height. If several bones crush and form wedge shaped fractures the spine can start to curve. Severe curvature of the spine can reduce the space under the rib cage, cause digestive and breathing problems and sometimes incontinence, as the internal organs are pressed on the bladder. Hip fractures are most common in older people, usually after a fall, and can have a big impact on quality of life.

Can I be tested for osteoporosis?

A simple X-ray of bone can highlight a fracture but osteoporosis only shows on an X-ray when at least 30% of your bone density has been lost.

A bone density scan, called a Dual Energy X-ray Absorptiometry (DEXA) scan, is used to measure the density of bones. This test is currently the most accurate and reliable means of assessing the strength of your bones and your risk of fracture. It is a simple, painless procedure that uses very low doses of radiation. You will be asked to lie down on the machine for 10-15 minutes whilst an X-ray arm passes over you to take an image of your spine and hip. Some centres have forearm machines which measure the density of the wrist. A bone density scan can diagnose osteoporosis, assess risk of fracture and monitor effects of treatment.

How can I get a bone density scan?

Bone density scans are only recommended for people who are at high risk of osteoporosis, so discuss your medical history with your doctor, who can decide whether to refer you to a hospital for a scan. Your doctor may use the results to decide on treatment for you, or you may be asked to see a specialist consultant.

What will the results tell me?

The results will show how your bone density compares to the average bone density of both a young adult of the same sex and someone the same age (and sex) as yourself. The results can be given as a percentage of the normal value, or as standard deviation, which means the number of units above or below the average for the population. If your bone density is between the normal range and the range defined as osteoporosis, this is called osteopenia, which means you have low bone density.

What is a bone-friendly diet?

Healthy bones need a well-balanced diet, incorporating minerals and vitamins from four different food groups, including bread and cereals; fruit and vegetables; milk and dairy products; meat, fish, eggs, pulses, nuts and seeds. You especially need to ensure that your diet is rich in calcium. Calcium is the most abundant mineral found in our bones and helps to give them strength and rigidity. Men and women need different amounts of calcium at different stages of life.

Good sources of calcium are milk and dairy products such as cheese and yogurt. Don't worry if you are watching your weight or cholesterol as low-fat varieties contain just as much calcium as their full-fat counterparts. If you don't like or are unable to eat dairy products, you should be able to get enough calcium from non-dairy sources but it might take a bit more planning. Non-dairy foods such as bread, green leafy vegetables and baked beans all contain calcium. Be careful not to have too much animal protein, salt or caffeine because in excessive quantities these can reduce your body's ability to absorb or retain calcium.

Vitamin D is needed to help the body absorb calcium. Although foods such as dairy produce, margarine and fish oils contain vitamin D, the major source of this vitamin is from the action of sunlight on skin. About 15-20 minutes of sunlight a day on the face and arms during the summer months is adequate to enable the body to store enough vitamin D to last the rest of the year. Be careful not to stay out in the sun too long to avoid burning or increasing your risk of developing skin cancer. Elderly people living in nursing homes who rarely get outside may become deficient in vitamin D; supplements of calcium and vitamin D may then be needed.

How to get enough calcium?

Milk, cheese and yogurt are good sources of calcium because they are readily available, and contain high amounts of calcium. There are also other foods which contain high levels of calcium, such as bony fish or tofu and useful amounts are found in vegetables like broccoli and spinach, dried fruits such as figs or apricots and nuts and seeds. For children who are reluctant to eat dairy products, calcium can also be obtained from foods like baked beans, pizza or ice-cream. Adding a cheese topping or a cheese or yoghurt sauce to meals can also help to boost daily calcium intake. Most people should be able to get enough calcium from their diet, but for people who find this difficult, calcium supplements are an alternative. Calcium and vitamin D supplements in the elderly have been shown to reduce bone loss and fractures.

Osteoporosis treatment

For people who have been diagnosed with osteoporosis, there are a range of treatments available to help prevent bone loss:

1 Hormone replacement therapy (HRT), is a common means of preventing and treating osteoporosis in women. Taking HRT also helps to greatly relieve distressing menopausal symptoms such as hot flushes, night sweats, headaches and vaginal dryness. Some women may experience side effects such as breast tenderness and temporary nausea but these symptoms usually stop after the first few months or with a change of the type or dose of HRT. There are over 30 forms of HRT available in pills, patches, implants or gels. HRT does not prevent heart disease. If it is taken for not longer than 2 years, it does not appreciably increase your risk of developing breast cancer.

2 Bisphosphonates are non-hormonal drugs for osteoporosis which work by "switching off" the cells that break down bone, allowing the bone building cells to work more efficiently. There is solid evidence that bisphosphonates like alendronate (Fosamax) and risedronate (Actonel) are effective in reducing loss of bone mass and reducing the risk of fracture. Fosamax is also licensed for the treatment of osteoporosis caused by corticosteroids and for the prevention of osteoporosis in women who have low bone mass (osteopenia).

3 Calcium and vitamin D supplements are an effective treatment to reduce bone loss in the elderly. Most people should be able to obtain adequate calcium in their diet but supplements are an alternative for people who find this difficult. Calcium alone has a limited effect as a treatment for osteoporosis but combined with vitamin D, it is particularly helpful for the elderly and housebound who cannot obtain natural sunlight and may have a poor diet.

4 Calcitonin is a hormone made by the thyroid gland which prevents the cells that break down bone from working properly, improving the action of bone building cells. Currently, calcitonin is available as an injection and as a nose apray. Because calcitonin has a pain killing effect it can be useful to use for a short time following a spinal fracture.

5 Testosterone is a treatment for men who are deficient in the male sex hormone, but it can also increase bone density in men with osteoporosis who have normal testosterone levels. It is available as injections or implants.

6 Anabolic steroids can increase bone and muscle mass and may be helpful in the very elderly who are frail and also in people with spinal fractures. Nandralone decanoate is the only anabolic steroid currently licensed for treating osteoporosis, and injections are carefully monitored due to side effects.

7 SERMs (Selective Estrogen Receptor Modulators) are a new generation of drugs which reduce the risk of osteoporosis and heart disease, but do not increase the risk of breast or endometrial cancers. One form, raloxifene (Evista), is licensed for the prevention and treatment of osteoporosis in post-menopausal women.


 

Copyright of Lee Chung Horn Diabetes & Endocrinology 2009