title: Megestrol acetate may stimulate the production of insulin-like growth factor 1 in breast tissues of women with breast cancer.
abstract: BACKGROUND
  In women with breast cancer who were treated with either continuous tamoxifen alone or sequential tamoxifen followed by megestrol acetate (MA), we demonstrated significant positive associations between the breast tumor estrogen receptor (ER) and an increase in serum sex hormone-binding globulin (SHBG) during tamoxifen treatment. We interpreted this as "ER uniformity" in different tissues, e.g., breast, liver. No other associations with ER were found. In the same study, the breast tumor progesterone receptor (PR) was determined. Our aim was to see if there were any associations between PR and endocrine changes during MA treatment.
  
  
  METHODS
  The breast tumor PR before treatment and serum insulin-like growth factor I (∂IGF-1), steroids, steroid-binding proteins, and insulin before and during treatment were measured in 17 postmenopausal women with breast cancer who were treated sequentially with tamoxifen 40 mg/day followed by MA 160 mg/day in alternating 3-month periods.
  
  
  RESULTS
  During MA treatment periods, the levels of IGF-1 and insulin increased significantly, whereas the levels of androgens, SHBG, corticosteroid-binding globulin, and cortisol decreased significantly. Significant positive correlations were found between the PR content and increments in ∂IGF-1 but not between PR and any other endocrine change.
  
  
  CONCLUSIONS
  PR expression in human liver is very weak, but malignant and normal breast tissues secrete considerable amounts of growth hormone and IGF-1 in vitro and in vivo. This activity is stimulated by progestogens. The association between PR and ∂IGF-1 may therefore reflect a direct PR-mediated action of MA on malignant and normal human breast tissues in vivo.
authors.affiliation: Division for Obstetrics and Gynecology, Department of Women's and Children's Health, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Mia
authors.initials: M
authors.lastname: Fahlén
authors.forename: Lars
authors.initials: L
authors.lastname: Löfgren
authors.forename: Eva
authors.initials: E
authors.lastname: von Schoultz
authors.forename: Sabine
authors.initials: S
authors.lastname: Naessén
authors.forename: Kjell
authors.initials: K
authors.lastname: Carlström
authors.forename: Gunnar
authors.initials: G
authors.lastname: Söderqvist
mesh_terms: D000368:Aged; D018931:Antineoplastic Agents, Hormonal / Q000627:therapeutic use*; D001940:Breast / Q000187:drug effects* / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D019290:Megestrol Acetate / Q000627:therapeutic use*; D008875:Middle Aged; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism; D013629:Tamoxifen / Q000627:therapeutic use*
chemical_list: D018931:Antineoplastic Agents, Hormonal; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D012738:Sex Hormone-Binding Globulin; D013629:Tamoxifen; D007334:Insulin-Like Growth Factor I; D019290:Megestrol Acetate