The risk of breast cancer is greater if levels of hormones estrogen or testosterone are higher in post-menopausal women, researchers from Brigham and Women’s Hospital reported in Breast Cancer Research, an open-access BioMed Central journal. The researchers examined six different growth and sex hormones and discovered that higher levels raised breast cancer risk by 16% for each one.

Dr Shelley Tworoger and team examined blood samples of nurses up to nine years before their breast cancer status was recorded. They matched post-menopausal females who had been diagnosed with breast cancer with two controls of the same age.

The following hormones were individually linked to a 50% to 200% rise in breast cancer risk:

  • Estrone – one of several natural estrogens.
  • Estradiol – one of several natural estrogens.
  • Testosterone – steroid hormone from the androgen group. Secreted in the testes of males and ovaries of females.
  • Androstenedione – a 19-carbon steroid hormone. An intermediate step in the biochemical pathway that produces testosterone, estrone and estradiol.
  • DHEA (Dehydroepiandrosterone) – a 19-carbon endogenous (originates from within the organism) steroid hormone. The most abundant circulating steroid in humans.
  • DHEA-sulfate – a metabolite of of DHEA.

The higher the number of hormones at elevated levels, the higher the breast cancer risk, the scientists found. For example, a woman with one elevated hormone may have a 10% higher risk when compared to those with normal levels, while women with five or six hormones with elevated levels would have double (100% higher) the risk. For those with seven or eight hormones at high levels, there can be triple the risk.

The risk was a little higher for females with estrogen receptor (ER) positive disease.

Dr Shelley Tworoger said:

“Elevated estrogens had the biggest effect on risk, especially for ER positive cancer. However, androgens, and prolactin also contribute to increasing risk of breast cancer.

These hormones are known to stimulate the growth of breast cancer cells in the lab and, while androgens can be converted to estrogen in the body, these hormones have also been found to stimulate cancer cell growth in the absence of ER.

Our results suggest that models used to assess breast cancer risk could be improved by taking into account multiple sex hormone and growth hormone levels.”

Written by Christian Nrodqvist