Scientists claim to have unearthed a cause of premature menopause - an enzyme which controls the rate at which women ovulate.

The international researchers have discovered the PTEN enzyme that keeps immature eggs from ripening prematurely. "It is a kind of brake," according to lead researcher Professor Ilpo Huhtaniemi of Imperial College, London [Images].

The researchers carried out an experiment on rodents and found that in those without PTEN in their eggs, the entire pool of immature eggs is activated prematurely, becoming ripe so the mouse uses up it store of eggs more rapidly.

The team is planning to investigate whether mutations in the PTEN gene are linked with premature menopause in women. "PTEN works in humans too. We have one good candidate to explain why some women develop premature menopause," Prof Huhtaniemi was quoted by The Daily Telegraph as saying.

In fact, according to the researchers, a drug to mimic the effects of PTEN could be used to prevent or treat premature menopause when combined with new tests that can show how quickly a woman's biological clock is ticking.

"By the same token, a way to block the effects of PTEN could lead to new ways to ripen eggs for IVF, notably if eggs fail to ripen in the first place," co-researcher Dr Kui Liu of the Umea University in Sweden said.

Lab-dish or 'in vitro' egg maturation has produced hundreds of babies worldwide, though is still experimental. "Now PTEN offers another way to ripen eggs. With the knowledge that PTEN suppresses follicle activation, it is in theory possible to culture a piece of the ovaries in the petri-dish and trigger the follicle growth with a synthetic PTEN inhibitor, which we have started to try," Dr Liu was quoted by the British daily as saying.

"Such a method will enrich the source of eggs for IVF or who want to freeze their embryos before going to have chemotherapy or radiation therapy for cancer," Dr Liu added.