The Relationship Between Hormones and Breast Cancer

Like normal, healthy cells, some breast tumors contain receptors for the hormones progesterone and estrogen, which send signals to the cells promoting continued growth. Approximately two out of three breast tumors are hormone receptor positive.

Estrogen-receptor-positive (ER+) tumors receive signals from and can grow when exposed to estrogen.

Progesterone-receptor-positive (PR+) tumors receive signals from and can grow when exposed to progesterone.

Breast cancer tumors that do not contain receptors for either estrogen or progesterone are known as hormone receptor negative.

Hormone therapy can be used to treat receptor positive tumors. Hormone therapy can help lower the levels of estrogen and progesterone in the body, and to block the hormones from signaling continuous cell proliferation (growth) in the tumors.

While some cases of breast cancer can be hereditary and result from specific gene mutations, such as the BRCA1 and BRCA2 genes, genetic and hereditary factors typically account for as little as 5% – 10% of all breast cancer diagnoses. Due to the relationship between estrogen and certain types of breast cancer, there are certain risk factors and lifestyle modifications that women should be aware of in order to understand and help mitigate their breast cancer risk as much as possible.

Factors such as the age a woman starts menstruating and begins menopause can increase breast cancer risk. An earlier period and later menopause expose the body to estrogen for longer periods of time for example, increasing cancer risk. Hormone therapy that includes estrogen and progesterone can also potentially increase a woman’s breast cancer risk.