NEW YORK (Reuters Health) - High levels of human chorionic gonadotropin (hCG), a hormone that is produced in early pregnancy, may lower a woman's risk of breast cancer, according to a report in the American Journal of Epidemiology.

Childbearing provides lifetime protection against breast cancer, the authors explain, but the biologic reasons for this benefit are not understood.

Researchers in Europe and the United States, led by Dr. Annekatrin Lukanova at the German Cancer Research Center in Heidelberg, used data from the Northern Sweden Maternity Cohort to address the theory that elevations in circulating hCG and alpha-fetoprotein during the first trimester of pregnancy have a long-term protective effect against breast cancer risk.

The researchers found no overall association between breast cancer and either hormone. They did find, however, that there was a trend toward lower breast cancer risk for women with the highest hCG levels, compared with women with the lowest levels.

The protection afforded by higher hCG levels was limited to women diagnosed after the average lag time to cancer diagnosis, which was 14 years, the report indicates.

Alpha-fetoprotein concentrations were not associated with breast cancer risk in any of the overall or subgroup analyses.

"Although the results of the current study must be regarded as suggestive and should be interpreted with caution, they are consistent with a protective effect of elevated hCG levels during pregnancy on long-term risk of breast cancer," the investigators conclude.

SOURCE: American Journal of Epidemiology, December 1, 2008.

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