NEW YORK (ASRN.ORG)- Women who undergo hysterectomies often have both ovaries removed along with the uterus in order to prevent ovarian cancer. But a new study suggests ovary removal may increase the risk of another seemingly unrelated ailment, lung cancer.

University of Montreal scientists stumbled onto the connection while investigating the relationship between lung cancer and hormones in women. They found no relationship between hormonal factors like menstruation patterns, child bearing or breast-feeding histories and the risk of lung cancer. The researchers did, however, discover that women whose menopause had been induced medically were at 1.92 times greater risk of developing lung cancer than women who had experienced natural menopause.

"We were surprised - we had no prior expectation of this finding," said Anita Koushik, a researcher. "Aside from the fact that smoking increases your risk of lung cancer, the results of this study suggest that having a non-natural menopause contributes to an almost doubling of the risk." She noted, though, that the findings could have occurred by chance.

The vast majority of women who had experienced a non-natural menopause had had both ovaries surgically removed, she added.

While smoking is the leading cause of lung cancer, other factors may play a role in enhancing the impact of the carcinogens in tobacco, Dr. Koushik said. In women, these factors could be hormonal. Both normal and cancerous lung tissue express estrogen receptors and may be influenced by levels of the hormone in the body, Dr. Koushik said. The patterns of expression are different in men and in women.

Medically induced menopause usually occurs at a younger age than natural menopause. Surgical menopause results in a sudden drop in estrogen levels, compared with the more gradual decline in hormone levels that occur with natural menopause. Dr. Koushik suggested the increased lung cancer risk maybe linked to the impact of plummeting hormone levels.

In the study, the scientists examined data on 422 women diagnosed with lung cancer in the greater Montreal area in 1996 and 1997 and compared them with 577 randomly selected control subjects. The women were asked about a variety of hormone-related factors, including when they got their first periods, how many children they had, whether they breast-fed their children and whether they had gone through menopause. The researchers also gathered detailed information about smoking, occupational history, education, and family income.

The report is not the first to link ovary removal with an increased risk of lung cancer. A recent analysis of data reported that women who had had hysterectomies but kept their ovaries lived longer than women who had had the procedure but whose ovaries were removed.

While those who had their ovaries removed were less likely to develop breast cancer and virtually eliminated their risk of ovarian cancer, they were more prone to heart disease and were at greater risk for other kinds of cancer, including a doubling of the risk for lung cancer among those women who never used hormone therapy.

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