Osteoporosis

Overview

Osteoporosis is a thinning and weakening of the bones, usually associated with ageing. The bones hold most of the body’s calcium and the remaining amount circulates for use by other tissues. Bone is constantly breaking down and reforming. With osteoporosis, the amount of calcium present in the bone slowly decreases, causing the bones to become brittle and prone to fracture. Often, the diagnosis of osteoporosis is not made until a bone is broken with only moderate pressure.

People at increased risk include women with an early menopause or with removal of ovaries, women who have never given birth and those who are anorexic. Men at risk include those with decreased testosterone levels due to treatment for cancer. Men and women who have a family history of osteoporosis or who have taken high doses of steroids for long periods are also at risk.

About Osteoporosis

Tests

The most common way to diagnose osteoporosis is to have a bone density scan with a machine known as a DXA (Dual energy X-ray Absorptiometry) scanner. Usually the hip and spine are scanned using low doses of radiation. The measured bone density is compared with the average to produce a score which if minus 2.5 standard deviations (SD) or less indicates osteoporosis.

If you are being investigated for osteoporosis, a blood sample may be taken to measure certain mineral and hormone levels. Blood calcium levels are usually normal in osteoporosis. Alkaline phosphatase (ALP), an enzyme from liver and bone, usually shows normal activity in osteoporosis. Tests of thyroid function (TFT) may be performed to identify abnormal thyroid function. Hormones produced by the brain (LH and FSH) and ovaries (oestradiol) or testicles (testosterone) may be measured to identify any deficiency. Protein levels may be examined in both blood and urine to identify multiple myeloma, a type of cancer associated with bone breakdown. Products of bone turnover are called bone markers and can be measured in blood and urine. Measurement of these 'bone resorption' and 'bone formation' markers may be useful when monitoring the response to treatment with drugs which slow down bone breakdown.
Prevention

Whilst complete prevention of osteoporosis may not be possible, measures can be taken to reduce bone loss. These measures include regular weight-bearing exercise and calcium and vitamin D supplements (or food rich in these), stopping smoking and reducing coffee and alcohol intake. People should not wait until they are older to start these preventive activities.

There is evidence that hormone replacement therapy may lower the risk of osteoporosis in women by increasing bone density, reducing the number of fractures, and improving balance. However, there are risks associated with this therapy, including an increased risk for uterine and breast cancers and blood clots. Other treatments available include drugs called bisphosphonates which reduce bone breakdown, and selective oestrogen receptor modulators. These drugs maintain bone density and reduce the risk of having fractures.