Professor David W Purdie MD, FRCOG, FRCP Ed,

Edinburgh Osteoporosis Clinic

Osteoporosis is a relatively new problem. The elimination of many of the infectious diseases that used to shorten our lives has led to the identification of this, and other diseases of the elderly. Longer ago we concentrated on life-expectancy - today we are increasingly concerned with health-expectancy. Osteoporosis symptoms include loss of stature: reduced height and curvature of the spine; and general skeletal fragility causing fracture after minor trauma.

The 204 bones in the human body reach peak strength at age 25 and continue to consolidate until around 40. At this stage our bones start to weaken. As Oestrogen is a natural bone protector women can experience an acceleration of bone density loss during the ten years around menopause as oestrogen levels are reduced.

There are 2 types of bone. Examples of each are:

1. The leg: a shaft of compact bone surrounding the shock-absorbing trebecular bone. Weakness occurs in the neck of the femur and can lead to hip fracture.
2. The spine: a trabecular (honeycomb) structure, with a shell of compact bone. Its strength is in its ability to distribute shock - like chain mail armour.

Bone renewal is dynamic: osteoclasts burrow into existing bone to create cavitiesa that are re-filled by bone-building osteoblasts. As we get older the osteoblasts weaken and are no longer able to fill the holes created for them. Over time, the trabecular bone weakens to breaking point and the gaps within the honeycomb structure widen, giving a more lacy porous appearance.

Today osteoporosis is detectable by the DXA bone scan, a specialised x-ray at bone level. Ideally, bone scans should be available in all general hospitals. In the USA, all women over 65 qualify for a free scan. In the UK only those at risk are advised to get a scan. These include:

• Women who have early menopause
• Medical suspicion i.e., those appearing to lose height or who have a suspiciously easy fracture
• Radiological suspicion i.e., symptoms spotted during other medical scanning tests
• People using more than 5mg Prednisolone per day (steroid users)
• Family history - anyone who has a 1st degree relative with the disease

Scans should be repeated every 5-10 years if initially in good shape. People who display some symptoms may be asked to return sooner in order to monitor their condition.

If you have been refused a scan, treatment can be offered on clinical grounds e.g., if an easy fracture has occurred or height lost.

Women in menopause may be prescribed HRT, replacing some of the natural oestrogen. There is currently publicity around an increase risk of breast cancer for women on HRT. This risk is small: women should weigh up both sides, understand the implications of taking or not taking HRT on their bones, and the risk of cancer and decide their best course of action.

Treatments available are:

• SERMs (selective oestrogen receptor modulators)
• Biphosphonates
• Strontium

There are things we can do to help our bones to keep healthy

• Eat a good diet, rich in calcium which promotes bone growth throughout our lives.

  In childhood ½ pt of semi-skimmed milk, 1 tub of yoghurt or 1oz of hard cheese provide a day’s calcium need. Pizza, cheese, smoothies and lattes are all good sources of calcium.

  Only take supplements if you are not able to eat enough of the right food. Any extra cannot be stored and is just excreted. Vitamin D promotes the absorption and retention of calcium.

• Use your skeleton

Regular exercise helps to keep bone healthy. Weight-bearing exercises and swimming are recommended.

The National Osteoporosis Society has excellent publications for the general public on the subject - www.nos.org.uk