Effect of tamoxifen on serum insulinlike growth factor I levels in stage I breast cancer patients.
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.
Pollak
M
M
Department of Oncology, Jewish General Hospital, Montreal, Canada.
Costantino
J
J
Polychronakos
C
C
Blauer
S A
SA
Guyda
H
H
Redmond
C
C
Fisher
B
B
Margolese
R
R
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*
D013629:Tamoxifen; D007334:Insulin-Like Growth Factor I