AS PEOPLE, particularly women, grow old, they shrink. The humped back is the result of osteoporosis - a potentially lethal disease in which the bone mass withers. But now, a new generation of drugs, bone "paste" and hormones may soon bring relief.

Osteoporosis affects 200 million people worldwide. In its advanced stages, bones become so brittle that even a cough or a sneeze could lead to a fracture. Osteoporosisinduced hip fracture kills about 20 per cent of affected women. It is an expensive disease to treat. It costs the us between us $7410 billion every year. Current treatment can help prevent further loss of bone but not even a miracle can reverse bone loss once it has occurred.

Recently, Norian, a California-based company, announced that it had invented an artificial bone paste, the Norian SRS, that could help fill the gaps in osteoporosis-weakened bones. The. com- pound - a mixture of phosp , oric acid and sodium phosphate - is undergoing human trials in the US.

"Think of it as being the mortar between bricks," says the paste's inventor, Brent R Constantz. The paste is injected into fractures with a syringe. In about 10 minutes, it sets into a kind of internal cast to stabilise the realigned bones. In another 12 hours, it becomes as strong as the bone itself, before gradually disappearing as the patient's own bone cells grow to replace it.

Another us-based pharmaceutical company, Merck, also claims to have developed a drug - alendorate - for osteoporosis treatment. This drug, which focuses on building up bone mass rather than preventing bone loss, is awaiting us Food and Drug Administration's (FDA) approval.

Calcium regulatory drugs are being developed by NPS Pharmaceuticals, a Utah-based company, in collaboration with SmithKline Beecham. While one mimics the effect of calcium to suppress resorption of bone into the body, the other increases natural secretion of calcitonin, a hormone that reduces resorption. Calcitonin, earlier injected, is now available as nasal sprays.

A recent study at the University of California in San Francisco (UCSF) claims to have fo@nd that laboratory animals treated with naturally-occurring parathyroid hormone - which aids calcium metabolism, regain bole mass lost.

"'The treament with this hormone ... is the first found to be successful in reversing the damage caused by osteoporosis," says Nancy Lane, UCFS assistant professor of medicine and lead author of the study.

In a related development, the us-based Eli Lilly, which has developed a synthetic hormone raloxifene - hopes to file it with the FDA by year end. Researchers believe that raloxifene is more an overall health drug; it targets oestrogen receptors in the heart and bone but not the reproductive system, thus curing heart disease as well as osteoporosis. Its advantage over oestrogen is that women do not experience a return of their menstrual cycle.

So far, osteoporosis could only be detected by comparing x-rays taken over a number of years to check bone mass loss. A new diagnostic test called Biomarkers, will speed up the process by detecting degraded bone in blood or urine. But it will not be able to assess bone mass or identify the person at risk.

Oestrogen therapy has very low rates of compliance. Patients are also concerned that the drug may be linked to breast cancer, although studies have so far been inconclusive.

Compliance is a major factor in osteoporosis treatment. Drugs are to be taken much before the disease becomes apparent. Unfortunately, the absenci of symptoms leads people to truncate the drug course, and by then it is much too late to prevent the disease.