Testosterone Linked to Higher Rate of Colon Cancer in Males

Results of experiments carried out with two established animal colon cancer models indicated that the male hormone testosterone was responsible for males having a greater likelihood of developing the disease.

It has been recognized recently that men develop colonic adenomas and carcinomas at an earlier age and at a higher rate than women. This sex susceptibility also occurs in the ApcPirc/+ (Pirc) rat model of early colonic cancer, with male Pirc rats developing twice as many adenomas as females. The ApcMin/+ mouse also shows enhanced male susceptibility to cancer formation, but only in the colon.

Investigators at the University of Missouri (Columbia, USA) worked with these two rodent populations to determine whether the males' natural high levels of testosterone or the lack of female hormones was related to the increased development of colon cancer.

They reported in the November 3, 2014, online edition of the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS) that removing testosterone from the rodents by castration caused colon cancer rates to decrease dramatically. Restoration of testosterone by dietary supplementation restored the tendency for cancer development. In contrast, removal of the ovaries, which eliminated female hormones, did not cause an increase in rate of cancer development. Dietary supplementation of female hormones also failed to have any effect.

“Previously, scientists believed that female hormones may have lent some sort of protection against tumor susceptibility,” said first author Dr. James Amos-Landgraf, assistant professor of veterinary pathobiology at the University of Missouri. “However, by showing that removing testosterone from rats leads to a drastic decrease in colon cancer susceptibility, it appears that male hormones may actually contribute to colon tumor growth rather than female hormones being protective. All women have some level of testosterone in their bodies naturally, but those levels typically are much lower than estrogen and other female hormones. Once women experience menopause and their female hormone levels decrease, their testosterone levels become relatively higher. This corresponds to the time when they begin to experience higher rates of colon cancer and could be a sign of a relationship between testosterone levels and colon tumor growth.”

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