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Research Summary
After the WHI trial was stopped it was widely reported that the patients
receiving combined treatment with estrogen and progestin had a higher
incidence of breast cancer than the group receiving estrogen alone,
however, bioidentical progesterone was not used in this
study. Bioidentical progesterone has been found not to increase the risk of
breast cancer when used in combined hormone therapy with estrogens, while
synthetic progestins did increase the risk (Fournier et al. 2005).
Endogenous progesterone levels were found not to increase breast cancer risk
in the first study to investigate this in postmenopausal women; this was true
even for progesterone receptor positive tumors, which were the most strongly
affected by all circulating steroid hormones measured except for progesterone
(Missmer et al. 2004). On the other hand, higher levels of endogenous
estrogens and androgens were significantly correlated with increasing breast
cancer incidence. Kaaks et al. (2005) also found a significant
reduction in breast cancer risk in women with high progesterone levels.
There is evidence that women with progesterone deficiency have a
markedly increased incidence of breast and other cancers (Cowan et
al. 1981), and also that the application of progesterone cream to the breasts
decreases proliferative activity in breast tissue while estradiol cream
increases such activity (Chang et al. 1995). In a study of women undergoing
breast tumor excision, those who had higher levels of circulating
progesterone at the time of excision had a significantly improved prognosis,
the authors concluding that the tumor tissue was not in an actively
proliferating state at the time of excision because of progesterone’s
antiproliferative effects (Mohr et al. 1996).
The role of hormone balance in the development and prevention of breast
cancer is still a subject of much controversy. More research is needed in
this area. An interesting discussion that is on the edge of new thinking
about the role of natural and synthetic hormones in the biochemistry of
breast cancer can be found in the book “What your doctor may not tell you
about breast cancer – how hormone balance can help save your life” by JR
Lee, D Zava and V Hopkins, Warner Books, New York 2003.
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Categories available are: Androgens;
Estrogens;
Progesterone;
Bone:
Brain;
Breast;
Cardiovascular;
Formulations;
Menopausal
Symptoms; Premenopause;
Progestin;
Safety;
Uterus.
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1. - The
Bioidentical Hormone Debate: Are Bioidentical Hormones (Estradiol,
Estriol, and Progesterone) Safer or More Efficacious than Commonly Used
Synthetic Versions in Hormone Replacement Therapy? Holtorf
K.
Postgrad Med 2009;121(1):1-13.
This literature review presents the substantial evidence for the safety
and efficacy of bioidentical hormone therapy, including estradiol,
estriol, and progesterone, which shows that it presents lower risks for breast cancer and cardiovascular disease than
synthetic or animal-derived hormones. Studies show that progestins have a
number of negative effects on the cardiovascular system and an
association with breast cancer risk that can be avoided by using
bioidentical progesterone.
Not available on Pubmed
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2. - A
comprehensive review of the safety and efficacy of bioidentical hormones
for the management of menopause and related health risks.
Moskowitz D.
Altern Med Rev. 2006 Sep;11(3):208-23.
This review describes the various synthetic estrogens and progestins used
in hormone replacement therapy and discusses their safety in relation to
natural alternatives. Natural estrogens and progesterone are being
increasingly used in clinical practice and have demonstrated
effectiveness in treating menopausal symptoms. They also have improved
safety profiles with respect to breast
cancer risk and cardiovascular effects.
Article
on Pubmed
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3. - Part 3 - The science behind bioidentical
hormone replacement therapy. Wepfer ST.
Int J Pharm Compounding 2002;6(2):142-6
Differences between synthetic progestins and bioidentical progesterone in
terms of their effects on breast cancer
risk, estrogen dominance, and vasomotor symptoms are discussed. The
review also covers the use of testosterone for postmenopausal women who
have androgen deficiency because of surgically induced menopause.
Androgen deficiency is also seen in women receiving estrogen replacement
therapy, which reduces bioavailable testosterone because it increases
levels of sex hormone binding globulin in the blood. The author concludes
that bioidentical hormones are more effective and safer than the
synthetic alternatives, but hopes that large trials will soon be
conducted to confirm their promising effects.
Link to Abstract
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Progesterone and Breast Health 