Study links smoking with infertility and early menopause
( 2001-07-16 10:02 ) (7 )

Women who smoke are running the risk of becoming infertile and inducing an early menopause, according to the latest US scientific report to investigate a link already suspected by researchers.

"We've uncovered a mechanism to explain why premature ovarian failure occurs following exposure to toxic chemicals in the environment," the head of the study at Boston's Massachusetts General Hospital says in the report to be published in the August issue of Nature Genetics.

"We've correlated this (the earlier menopause in female smokers) with exposure to a class of chemicals in tobacco smoke that accelerate the death of egg cells in the ovaries," said Jonathan Tilly.

The research adds two more serious medical effects to a catalogue of illnesses and diseases scientifically proven to be caused by smoking, the study says.

Research carried out on mice confirms the long suspected link between female infertility and a class of toxic chemicals known as polycyclic aromatic hydrocarbons (PAHs), which are present in tobacco smoke and cause the destruction of eggs in the ovaries.

The toxic chemicals are also released into the environment by fossil fuel combustion.

These chemicals bind to a receptor inside egg cells of the ovaries causing the release of a gene which then sets off a suicide command ordering the egg to undergo programmed cell death.

But eggs from mice engineered to lack either the receptor or the gene were not affected by the toxic chemicals in the same way, showing the importance of both the gene and the receptor in premature ovarian failure.

Scientists then grafted tissue from human ovaries under the skin of mice, to prove that the research carried out on mice would have similar effects on humans.

When the mice were given an injection of the toxic compound, researchers reported a striking increase in degenerating eggs and programmed cell death in the human ovarian tissues, in the same way that they observed in mice ovaries.

"The data strongly support the hypothesis that the early onset of menopause in women smokers is caused, at least in part, by the actions of tobacco smoke-derived PAHs (toxins) in human oocytes" -- eggs before they mature, Tilly says.

He added that he hopes the technique of grafting human tissue onto the mice will allow for further research on the effect of other potential biohazards and drugs on the health of women's eggs.

The report will be available online from Monday.