What is osteoporosis?

Bone density reduces to some degree in all people as they age. Osteoporosis is a condition where the bones become excessively thin and weak, such that there is a greater risk of fractures. It affects more than 50% of women and about 30% of men over 60 years, as well as a few younger people.

Osteoporosis is often called the ‘silent disease’ as it can develop without any symptoms, until you find you have broken a bone.

How does bone grow?

Bone is a living tissue that grows in a porous mesh-like structure. Throughout life the body breaks down old bone and rebuilds new bone in a continuous cycle. We gain bone by building more than we lose.

Bones contain the protein collagen and minerals such as calcium and phosphorus, which make the collagen hard and dense. To maintain bone density, the body needs adequate calcium and other minerals and certain levels of hormones, including oestrogen in women and testosterone in men.

Vitamin D is needed so the body can absorb calcium from food and incorporate it into bones. Physical activity also helps bone become dense.

Interior of healthy bone.	Interior of thin, porous bone.

How does bone become thinner?

Bones grow more and more dense until around the age of 30. After about 40, bone breaks down slightly faster than it is replaced and bones slowly become less dense.

In women, after the menopause, the ovaries stop releasing eggs and the level of oestrogen decreases. Over many years, a low oestrogen level causes the inner mesh of bones to become thinner, weaker and more brittle. In men, this can happen if there is too little testosterone.

Am I at risk for osteoporosis?

Some people are more at risk than others. The following risk factors are linked to having osteoporosis, or getting it later on. The more of these that apply to you, the more important it is to discuss osteoporosis with your doctor:

• being female
• previous fracture due to osteoporosis
• family history of osteoporosis
• being aged 50 years or older
• being past the menopause
• having your ovaries removed or reaching menopause before the age of 45
• being thin or ‘small boned’
• White (Caucasian) or Asian ancestry
• too little calcium in your diet - less than four servings of dairy products a day (choose low fat options)
• smoking
• alcohol (more than four standard drinks a day)
• less than 30 minutes outdoors in sunlight each day
• less than 30 minutes of physical activity each day
• long term use of some medications, such as steroids (eg, cortisone, prednisone) or anticonvulsants.

The last six of these are the risk factors you can modify or have some control over throughout your life to reduce the chances of osteoporosis in old age. For osteoporosis, prevention is far more successful than treatment.

How can my doctor help?

Your doctor can assess your risk for osteoporosis from your medical history and by asking you about your lifestyle. Physical signs that you may have weak bones include previous fractures (often of the wrist, hip or spine), a loss of height or stooping, and a curved spine. Your doctor may suggest you have a bone density scan (a type of x-ray) to check for bone weakness.

What can be done about osteoporosis?

If you have weak bones there are practical steps you can take in consultation with your doctor - these depend on your age, gender, medical history and the degree of bone thinning. These measures will help you avoid a fracture and maintain your quality of life. Unfortunately, once you have had one osteoporotic fracture, you are more likely to have others.

Weight-bearing exercise, such as walking or climbing stairs, can help bone become denser. It is a good idea to start this after having a check up with your doctor. Stopping smoking and drinking only small amounts of alcohol also helps prevent further bone loss.

To reduce your risk of injury in day-to-day life:

• plan your movements
• avoid straining your back or falling by, for example, wearing slip-proof shoes, putting slip-proof mats in the bath and shower, and always holding handrails
• be careful when lifting, bending or reaching
• use any cane or walker correctly and consistently
• if you fall, make sure you are unhurt before moving
• if you fall, ask your doctor to check your health; your eyesight or medications may need checking.

Treatments for osteoporosis

There is no complete cure for osteoporosis, but there are supplements and medicines that can increase bone thickness and reduce fracture risk. You can talk to your doctor about these before deciding which to try.

• Calcium supplementation - typically 1000mg daily - slows bone loss but does not usually stop it completely (loss of bone calcium is common in old age). A 250ml glass of milk contains about 300mg calcium - aim for low fat dairy options. Some people may find taking calcium tablets easier than having four dairy portions a day.
• Vitamin D (calciferol) supplementation can correct vitamin D deficiency, which is common in older people who are seldom outdoors. Vitamin D helps you absorb the calcium in your diet and your bones to utilise it.
• Calcitriol is also a form of vitamin D that helps the body absorb calcium and incorporate it into bone. Supervision by a doctor is needed as it can raise calcium too much.
• Bisphosphonates are bone-specific medicines that increase bone density and reduce fractures. They are currently the preferred treatment for osteoporosis. It is important to take the tablets as advised; that is, on an empty stomach with plenty of water (not tea, coffee or juice), remaining upright and not taking other foods or medications for half an hour, to avoid possible indigestion. Some patients take bisphosphonates as a once-yearly intravenous infusion.
• Hormone replacement therapy (HRT) is a long-established treatment for osteoporosis in women with low oestrogen levels (usually due to the menopause). HRT increases bone density and reduces fracture rates. However, it also increases the risks of blood clots, breast and uterus cancer, heart attacks and strokes, in older postmenopausal women in particular. For these reasons, HRT use is not widely recommended for osteoporosis, but it may be used for short term treatment of menopausal symptoms at the start or in early menopause. Men with low testosterone levels may benefit from testosterone replacement.

Original material provided by UBM Medica (NZ) Ltd. Updated in November 2007.

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