title: Estrone - a partial estradiol antagonist in the normal breast.
abstract: Oral hormone replacement therapy (HRT) based on estradiol-17β (E2) greatly increases circulating estrone (E1) levels. E1 is an estrogen receptor agonist but may also be a partial E2 antagonist. We investigated the effects of circulating E1 on the association between circulating E2 and the increase in mammographic density (∂MD) in 46 healthy post-menopausal women treated with E2 2 mg and norethisterone acetate 1 mg daily. MD and serum E1 and E2 were measured before and after 6 months of treatment. At high E1 levels, ∂MD showed significant positive correlations leading to increase (∂-values) in both E1 and E2. Lowering the upper serum E1 limit strengthened the correlations to ∂E2 while the significant correlations to ∂E1 disappeared. E1 at high concentrations may act as a partial E2 antagonist also in the normal breast in vivo and disturb relationships between circulating E2 and biological estrogen effects. When investigating the relations between circulating steroids and their effects, structurally related compounds, which may act as partial antagonists, have to be considered, at least when they are present in higher concentrations.
authors.affiliation: a Division of Obstetrics and Gynecology, Department of Woman's and Children's Health , Karolinska Insitutet, Karolinska University Hospital , Solna , Sweden and.
authors.forename: Eva
authors.initials: E
authors.lastname: Lundström
authors.affiliation: a Division of Obstetrics and Gynecology, Department of Woman's and Children's Health , Karolinska Insitutet, Karolinska University Hospital , Solna , Sweden and.
authors.forename: Peter
authors.initials: P
authors.lastname: Conner
authors.affiliation: a Division of Obstetrics and Gynecology, Department of Woman's and Children's Health , Karolinska Insitutet, Karolinska University Hospital , Solna , Sweden and.
authors.forename: Sabine
authors.initials: S
authors.lastname: Naessén
authors.affiliation: b Department of Surgery , Capio St Görans Hospital , Stockholm , Sweden.
authors.forename: Lars
authors.initials: L
authors.lastname: Löfgren
authors.affiliation: a Division of Obstetrics and Gynecology, Department of Woman's and Children's Health , Karolinska Insitutet, Karolinska University Hospital , Solna , Sweden and.
authors.forename: Kjell
authors.initials: K
authors.lastname: Carlström
authors.affiliation: a Division of Obstetrics and Gynecology, Department of Woman's and Children's Health , Karolinska Insitutet, Karolinska University Hospital , Solna , Sweden and.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Söderqvist
mesh_terms: D000368:Aged; D001940:Breast / Q000187:drug effects*; D000071060:Breast Density; D001943:Breast Neoplasms / Q000097:blood* / Q000139:chemically induced / Q000000981:diagnostic imaging; D003276:Contraceptives, Oral / Q000009:adverse effects / Q000494:pharmacology*; D004338:Drug Combinations; D004958:Estradiol / Q000009:adverse effects / Q000097:blood* / Q000494:pharmacology; D004964:Estriol / Q000009:adverse effects / Q000494:pharmacology*; D004965:Estrogen Antagonists / Q000097:blood*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects; D004970:Estrone / Q000097:blood*; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities*; D008327:Mammography; D008875:Middle Aged; D009640:Norethindrone / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D003276:Contraceptives, Oral; D004338:Drug Combinations; D004965:Estrogen Antagonists; D004970:Estrone; D004958:Estradiol; C032040:Trisequens; D004964:Estriol; D009640:Norethindrone
keywords: Breast; E1 antagonist to E2; estrogens; hormone replacement therapy