Two months ago, a large team of scientists working on multiple continents published a research study that came to startling conclusions about breast cancer and natural progesterone. The team determined that unlike synthetic progestins, which increase breast cancer risks, natural progesterone has the potential to slow the growth of many breast cancer tumors or even shrink them.
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When sex hormones are tested in women either in saliva or blood spot, ZRT test reports give a ratio of progesterone (Pg) to estradiol (E2). The ratio is helpful in clinical practice when both E2 and Pg are within range, yet the patient continues to have symptoms. It is not expected to be normal or used clinically when either E2 and/or Pg are outside of their expected ranges or if the patient does not have clinical symptoms.
Editor’s Note: After the publication of Dr. David Zava’s last Health Watchers News and Views post, Hormone and Breast Cancer: the Latest Findings from the WHI, he received an attacking comment from a doctor who has been making claims for years that natural progesterone has the same effects as the synthetic progestins.
Although, as an editor, I do not publish comments that attack, Dr. Zava wrote an eloquent, if technical response which adds to the dialogue about progestins, progesterone and breast cancer. We share it here for the reading pleasure of hormone biochemistry geeks everywhere!
I very much disagree with the comment that “Progestins cause more breast cancer than estrogens because they act like progesterone.” Yes, synthetic progestins increase breast cancer, but there is no evidence that progesterone does the same. Quite the contrary. Below is my argument in favor of natural progesterone as a preventive for breast cancer, with reference to the Fournier studies that address this issue.