Progestin may modify the effect of low-dose hormone therapy on mammographic breast density

Progestogen safety and tolerance in hormonal replacement therapy

INTRODUCTION

Today, it is a mandatory practice to prescribe a combination of estrogens and progestogens for menopausal women requiring hormone therapy and with a uterus. The WHI study and its reanalysis demonstrate a big difference in results between the conjugated equin estrogen (CEE) only vs.CEE plus medroxyprogesterone acetate (MPA) arms in relation with breast cancer and cardiovascular risk. The conclusion is that risk is clearly higher in the arm with MPA than in the CEE only arm. Although the only progestogen used in the WHI study was medroxyprogesterone acetate, side effects and intolerance have been extrapolated as a class effect to all progestogens. Areas covered: Progestogen tolerance and side effects in hormone therapy were reviewed. For that purpose, a limited literature search was conducted on key resources including Pubmed, the Cochrane Library, ECRI, and major international health technology agencies. Expert opinion: Many of the tolerance effects are based on limited data. There are no double-blind randomized trials comparing long-term safety for breast cancer and cardiovascular risk among different progestogens. Short-term clinical studies, observational, and in animal and in vitro studies indicate that both micronized progesterone and dydrogesterone are the safer progestogens with an acceptable metabolic profile.

Estradiol plus drospirenone therapy increases mammographic breast density in perimenopausal women

OBJECTIVE

To investigate the effects of 17β-estradiol 1mg plus drospirenone 2mg (E2/DRSP) treatment on mammographic breast density in perimenopausal women.

STUDY DESIGN

In this prospective study, 80 healthy perimenopausal women aged 41-49 years were enrolled and assigned to either E2/DRSP (n=40) or a control group (n=40). Mammograms were performed at baseline and after 12 months of treatment. Mammographic breast density was quantified according to the Wolfe classification.

RESULTS

We demonstrated an increase in mammographic breast density in 37% (95% CI (confidence interval): 18.8-55.3%) of women treated with E2/DRSP after 12 months. The percentage of women with increased density was 0% (95% CI: 0.0-0.0%) in the control group. The difference in breast density between the E2/DRSP group and the control group was statistically very significant (p<0.001).

CONCLUSIONS

E2/DRSP therapy for 12 months in perimenopausal women significantly increased mammographic breast density in comparison to a control group. Further long-term and large scale prospective studies are needed to evaluate this issue.

Comparative analysis of the uterine and mammary gland effects of progesterone and medroxyprogesterone acetate

OBJECTIVES

In combined hormone replacement therapy (HRT) progestins are used to inhibit estradiol-activated uterine epithelial cell proliferation. In comparison to estradiol-only therapy, combined HRT leads to enhanced proliferation of mammary epithelial cells. In a quantitative mouse model, we assessed the balance between uterine and undesired mammary gland effects for two progestins that are widely used in HRT, progesterone and medroxyprogesterone acetate.

STUDY DESIGN

Mice were ovariectomized and after 14 days they were treated subcutaneously with either vehicle, estradiol (100 ng) or estradiol plus increasing doses of progesterone or medroxyprogesterone acetate for three weeks.

MAIN OUTCOME MEASURES

Measures for progestogenic mammary gland activity were stimulation of side-branching and stimulation of epithelial cell proliferation. Progestogenic activity in the uterus was assessed by measuring inhibition of estradiol-activated uterine epithelial cell proliferation. ED(50) and ID(50) values for the distinct readouts were obtained and dissociation factors for uterine versus mammary gland activity were calculated.

RESULTS

MPA demonstrated uterine activity and mitogenic activity in the mammary gland at the same doses. In contrast, progesterone showed uterine activity at doses lower than those leading to significant stimulation of epithelial cell proliferation in the mammary gland.

CONCLUSIONS

Progestins do not behave the same. Use of the natural hormone progesterone, but not MPA, in combined hormone therapy might offer a safety window between uterine effects and undesired proliferative activity in the mammary gland.