title: Comparative analysis of the uterine and mammary gland effects of drospirenone and medroxyprogesterone acetate.
abstract: The role of progestins in combined hormone therapy is the inhibition of uterine epithelial cell proliferation. The Women's Health Initiative study provided evidence for an increased risk of breast cancer in women treated with conjugated equine estrogens plus the synthetic progestin medroxyprogesterone acetate (MPA), compared with conjugated equine estrogens-only treatment. These findings continue to be discussed, and it remains to be clarified whether the results obtained for MPA in the Women's Health Initiative study are directly applicable to other progestins used in hormone therapy. In this study we compared in a mouse model the effects of the synthetic progestins, MPA, and drospirenone in two major target organs: the uterus and mammary gland. As quantitative measures of progestin activity, we analyzed maintenance of pregnancy, ductal side branching in the mammary gland, and proliferation of mammary and uterine epithelial cells as well as target gene induction in both organs. The outcome of this study is that not all synthetic progestins exhibit the same effects. MPA demonstrated uterine activity and mitogenic activity in the mammary gland at the same doses. In contrast, drospirenone behaved similarly to the natural hormone, progesterone, and exhibited uterine activity at doses lower than those leading to considerable proliferative effects in the mammary gland. We hypothesize that the safety of combined hormone therapy in postmenopausal women may be associated with a dissociation between the uterine and mammary gland activities of the progestin component.
authors.affiliation: TRG Women's Healthcare, Bayer Schering Pharma AG, Müllerstrasse 178, 13353 Berlin, Germany. christiane.otto@bayerhealthcare.com
authors.forename: Christiane
authors.initials: C
authors.lastname: Otto
authors.forename: Iris
authors.initials: I
authors.lastname: Fuchs
authors.forename: Helga
authors.initials: H
authors.lastname: Altmann
authors.forename: Mario
authors.initials: M
authors.lastname: Klewer
authors.forename: Alexander
authors.initials: A
authors.lastname: Walter
authors.forename: Katja
authors.initials: K
authors.lastname: Prelle
authors.forename: Richardus
authors.initials: R
authors.lastname: Vonk
authors.forename: Karl-Heinrich
authors.initials: KH
authors.lastname: Fritzemeier
mesh_terms: D000736:Androstenes / Q000494:pharmacology*; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D008297:Male; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D017258:Medroxyprogesterone Acetate / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010052:Ovariectomy; D011247:Pregnancy; D011255:Pregnancy Maintenance / Q000187:drug effects; D045167:Progesterone Congeners / Q000494:pharmacology; D014599:Uterus / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
chemical_list: D000736:Androstenes; D045167:Progesterone Congeners; D017258:Medroxyprogesterone Acetate; C035144:drospirenone