Hamburg  - German scientists claim to have found the molecular "switch" that activates osteoporosis, the crippling degenerative disease which afflicts millions of people, mostly older women.

The German researchers at the Max Delbrueck Centre for Molecular Medicine (MDC) in Berlin have found a molecular mechanism which regulates the equilibrium between bone formation and bone resorption, according to their report in the Journal of the European Molecular Biology Organisation (EMBO).

Until now, it was not clear exactly how the bone-loss disease develops.

Together with colleagues from the Netherlands and the US, researchers under Professor Achim Leutz from the Berlin-based Max- Delbruck Centre discovered that the observed disequilibrium between bone-forming cells (osteoblasts) and bone-resorbing osteoclasts is caused by an imbalance of two proteins.

Essentially, Professor Leutz has unlocked a complicated mechanism which maintains the equilibrium between bone formation and bone resorption.

The molecular imbalance suppresses this gene switch and thus enhances the proliferation and activity of the osteoclasts. As a result, the osteoclasts resorb more bone substance than is built by the osteoblasts. In other words, the body is not able to form new bone cells as fast as the old bone cells degenerate.

In osteoporosis, excessive bone resorption occurs. The bones lose their density and are therefore prone to breakage. Even minor falls can lead to serious bone fractures.

"In the future, it may be possible to develop new drugs that regulate the activity ... and, thus, remedy the disturbance in osteoclast function," Professor Leutz wrote in his report.

It is estimated that one in three women and one in 12 men over the age of 50 worldwide have osteoporosis. (dpa)