'Pill' hormone linked to lower ovarian cancer risk

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'Pill' hormone linked to lower ovarian cancer risk

By Amy Norton

NEW YORK, Jan 02 (Reuters Health) - Evidence suggests that women who use

birth control pills have a decreased risk of ovarian cancer. Now new

research has zeroed in on the hormone progestin as the reason why.

In a review of data from a large US study from the early 1980s,

investigators found that women who used combination oral

contraceptives--which contain both estrogen and progestin--had a lower

risk of ovarian cancer than non-users.

And birth control pill combinations that carried the highest progestin

potency also carried the lowest ovarian cancer risk. Progestin is a

synthetic version of the female hormone progesterone.

Dr. len M. Schildkraut of Duke University Medical Center in Durham,

North Carolina, led the study. The findings are published in the January

2nd issue of the Journal of the National Cancer Institute.

According to the researchers, their findings are in line with new Duke

research in macaque monkeys showing that animals given progestin had

heightened rates of cell death and turnover in the lining of the

ovaries. An acceleration in this process may make it more likely that

abnormal cells are pushed to commit suicide, thereby reducing cancer

risk.

Schildkraut's team reviewed data on 390 women with ovarian cancer and

close to 3,000 healthy women, all between the ages of 20 and 54. Women

who had used birth control pills for at least 3 months were compared

with non-users, and users were evaluated according to whether their pill

combinations had high or low levels of estrogen and progestin.

The investigators found that women on low-potency progestin were twice

as likely as those on high levels of the hormone to develop ovarian

cancer. Overall, pill users were less likely than non-users to develop

the disease. The lower risk was seen even among women who used pill

combinations for only a few months.

High-potency progestin formulations used by women in the 20-year-old

study included Demulen, Ovulen and Ovral, among others; low-potency

brands included Enovid, 5 mg; Enovid-E; and Norinyl 1+80.

Formulations used today, which contain lower levels of both estrogen and

progestin, were not studied. But preliminary research suggests

new-generation birth control pills are also linked to a lower ovarian

cancer risk, study co-author Dr. G. Moorman told Reuters

Health.

Ever since research linked birth control pills to lower odds of ovarian

cancer, experts have suspected that the protection can be explained by

reduced ovulation. In part, this is because other factors that cut a

woman's lifetime ovulation, such as pregnancy and breast-feeding, are

believed to lower ovarian cancer risk.

" This study suggests ovulation is not the sole reason, " Moorman said.

She added that although increased cell turnover in the ovaries may help

explain the effects of birth control pills, the mechanism is not fully

clear and needs more study. In addition, other, non-hormonal agents may

offer the same benefits as progestin did in this study.

Moorman said that vitamin D--which has been found to affect cell

division--is one potential agent to be studied.

The exact causes of ovarian cancer remain unknown. Older age and having

a close relative with the disease are established risk factors.

SOURCE: Journal of the National Cancer Institute 2002;94:32-38.