Progesterone protects against breast cancer.

Previously I have written about the breast protective effects of progesterone (not to be confused with progestogens, the synthetic form of progesterone.)

Here is more interesting information about this very important issue for women, seeing as progesterone is in most of the script I write for menopausal women.

See also:


Progesterone protects against Breast Cancer.


The protective side of progesterone

Gianluigi Ferretti*, Alessandra Felici and Francesco Cognetti

Author Affiliations

Division of Medical Oncology A, Regina Elena Cancer Institute, Rome, Italy

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Breast Cancer Research 2007, 9:402  doi:10.1186/bcr1792
See related commentary by Jerry, and related research by Rajkumar et al.,

The electronic version of this article is the complete one and can be found online at:

Published: 21 November 2007

© 2007 BioMed Central Ltd 


According to Jerry’s commentary [1], exogenous oestrogen and progesterone potently inhibit tumorigenesis, representing an interesting strategy to prevent breast cancer, but we feel that the concerns noted by Jerry deserve further comment.

According to the Million Women Study [2], when progesterone was included in the hormone replacement therapy (HRT) formulation, the odds ratio fell from 1.3 to 1.1, indicating a protective effect exerted by progesterone, though no significant difference in the relative risk of ovarian cancer was registered in the subgroups of women who used oestrogen only compared with those who used the combination. Long durations of use of unopposed oestrogen and of oestrogen plus progestin, especially sequential regimens, have been reported to be associated with increased ovarian cancer risk. In preclinical models, combined progestins circumvent the anti-apoptotic action of the long isoform of Fas-associating protein with death domain-like interleukin-1 beta-converting enzyme (FLICE)-like inhibitory protein, an anti-apoptosis mediator, representing an effective therapy for ovarian cancer cells [3]. In premenopausal women, combined oral contraceptives (OC) have been described to be effective at decreasing the risk of epithelial ovarian carcinoma, even though the strongest risk reduction has been associated either with low- or high-potency progestin formulations.

Some synthetic progestins, when added to oestrogen in HRT for menopausal symptoms, have been reported to increase the risk of breast cancer more than oestrogen alone. Progestin use in breast cancer survivors is associated with an increased breast cancer risk compared with its non-use [4]. However, outside pregnancy, progesterone endogenously produced or exogenously administered does not have a cancer-promoting effect on breast tissue. The greater breast cancer risk related to the use of HRT containing oestrogen and synthetic androgenic progestin (19-nortestosterone derivatives) could be due to the non-progesterone-like effects enhancing the oestrogen proliferative effect on oestrogen-sensitive cancer cells.

In postmenopausal women, progesterone is added to prevent the carcinogenic effect of oestrogen on the uterus [5]. In premenopausal women, the potency of the progestin in most OC appears adequate to provide a protective effect against endometrial cancer. Higher progestin-potency OC may be more protective than lower progestin potency OC among women with a larger body habitus. Progestagens counteract the adverse effect of oestrogens on the endometrium, the effect being greater the more days every month that they are added to oestrogen and the more obese that women are.

Finally, because hormones may play a crucial role in the development of breast, endometrial and ovarian cancer, the impact on cancer risk of progestins included in HRT or OC formulations remains a major interest.


FLICE = Fas-associating protein with death domain-like interleukin-1 beta-converting enzyme; HRT = hormone replacement therapy; OC = oral contraceptive.

Competing interests

The authors declare that they have no competing interests.


  1. Jerry DJ: Roles for estrogen and progesterone in breast cancer prevention.Breast Cancer Res 2007, 9:102. PubMed Abstract | BioMed Central Full Text |PubMed Central Full Text OpenURL
  2. Beral V, Million Women Study Collaborators: Ovarian cancer and hormone replacement therapy in the Million Women Study.Lancet 2007, 369:1703-1710. PubMed Abstract | Publisher Full Text OpenURL
  3. Syed V, Mukherjee K, Godoy-Tundidor S, Ho SM: Progesterone induces Apoptosis in TRAIL-resistant ovarian cancer cells by circumventing c-FLIP(L) overexpression.J Cell Biochem 2007, 102:442-452. PubMed Abstract | Publisher Full Text OpenURL
  4. Beral V, Million Women Study Collaborators: Breast cancer and hormone-replacement therapy in the Million Women Study.Lancet 2003, 362:419-427. PubMed Abstract | Publisher Full Text OpenURL
  5. Beral V, Bull D, Reeves G, Million Women Study Collaborators: Endometrial cancer and hormone-replacement therapy in the Million Women Study.Lancet 2005, 365:1543-1551. PubMed Abstract | Publisher Full Text OpenURL

About Dr Colin Holloway

Gp interested in natural hormone treatment for men and women of all ages

Posted on October 22, 2015, in Uncategorized. Bookmark the permalink. Comments Off on Progesterone protects against breast cancer..

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