title: Effect of tamoxifen on serum insulinlike growth factor I levels in stage I breast cancer patients.
abstract: Insulinlike growth factor I (IGF-I) has been shown to be a potent mitogen for breast cancer cells in vitro, and IGF-I receptors have been demonstrated on human primary breast neoplasms. In a randomized, placebo-controlled study, we document that administration of the antiestrogen tamoxifen to patients with breast cancer was associated with a statistically significant (P = .002) reduction in the serum level of IGF-I. The mean IGF-I level was 1.4 U/mL in the placebo-treated group and 0.9 U/mL in the tamoxifen-treated group. Because serum IGF-I level is growth hormone (GH) dependent and because data suggest that the pubertal surge in GH and IGF-I levels is sex steroid dependent, we speculate that the mechanism underlying our observation may involve blockade by tamoxifen of estrogen action in the hypothalamic-pituitary axis. We conclude that tamoxifen treatment reduces IGF-I levels and that this reduction may contribute to the therapeutic effect of the drug.
authors.affiliation: Department of Oncology, Jewish General Hospital, Montreal, Canada.
authors.forename: M
authors.initials: M
authors.lastname: Pollak
authors.forename: J
authors.initials: J
authors.lastname: Costantino
authors.forename: C
authors.initials: C
authors.lastname: Polychronakos
authors.forename: S A
authors.initials: SA
authors.lastname: Blauer
authors.forename: H
authors.initials: H
authors.lastname: Guyda
authors.forename: C
authors.initials: C
authors.lastname: Redmond
authors.forename: B
authors.initials: B
authors.lastname: Fisher
authors.forename: R
authors.initials: R
authors.lastname: Margolese
mesh_terms: D000368:Aged; D000375:Aging / Q000097:blood; D001943:Breast Neoplasms / Q000097:blood* / Q000188:drug therapy; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008875:Middle Aged; D009367:Neoplasm Staging; D013629:Tamoxifen / Q000494:pharmacology*
chemical_list: D013629:Tamoxifen; D007334:Insulin-Like Growth Factor I