Human prolactin (PRL) is a hormone produced by the anterior pituitary gland and by other tissues. Prolactin has various chemical forms and has about 300 functions. Prolactin receptors are historically related to growth hormone receptors and other hormone receptors. PRL has a role in development of the breast during pregnancy and plays a part in a number of reproductive functions in males and females. Mice cannot become pregnant without prolactin.
Prolactin plays a role in the development of cancer of the breast and the prostate in rodents. “There is now strong evidence for a causal role for PRL in human breast cancer.” From the Nurses Health Study women in the top quartile of blood PRL levels have a doubled risk of breast cancer, independent of estrogen levels.
Women with higher levels of prolactin have a higher risk of metastasis from breast cancers. Prolactin levels of women decrease with each pregnancy. (This may be the reason for increased breast cancer in women who have never been pregnant.) Oral contraceptives increase blood prolactin levels and breast cancer risk.
Prostate cancer seems to be increased by higher prolactin levels in mice. Androgen therapy increases prolactin production by prostate cells and can result in high prolactin blood levels (hyperprolactinemia) and prostate enlargement in mice. Prolactin in mice promotes precancerous regions in the prostate. PRL treatment increases the growth of human prostate cells. Research is being done regarding the genetic control of prolactin to see how this could be used for cancer therapy.
CONCLUSION: Prolactin is a hormone important in reproduction. There is growing evidence for the importance of prolactin in cancer of the breast and prostate. Treatments to block the effect of prolactin may be of benefit in the treatment of these cancers.
NOTE: Ask your doctor for a blood prolactin test, especially during painful periods. Vitex is an herb which can reduce prolactin levels to treat painful periods. Dopamine agonists reduce serum prolactin. Serotonin agonists increase serum prolactin.
High prolactin blood levels comprise hyperprolatinemia or hyperprolactaemia.
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