Estrogens exert route- and dose-dependent effects on insulin-like growth factor (IGF)-binding protein-3 and the acid-labile subunit of the IGF ternary complex.
We have previously shown that exogenous estrogens exert route-dependent effects on serum GH and insulin-like growth factor I (IGF-I) levels. IGF-I circulates as a ternary complex with IGF-binding protein-3 (IGFBP-3) and the acid-labile subunit (ALS). It is not known whether IGFBP-3 and ALS in blood are regulated by estrogen and, if so, whether this is also route dependent. In the present study we investigate the effects on IGFBP-3 and ALS of oral and transdermal estrogens (study 1), of different oral estrogen formulations (ethinyl estradiol, conjugated estrogen, and estradiol valerate; study 2), of different estrogen dosages (study 3) in normal postmenopausal women, and of oral estrogen in hypogonadal GH-deficient women (study 4). Administration of oral, but not transdermal, estrogen in normal postmenopausal women significantly decreased serum levels of IGFBP-3 and ALS (P < or = 0.005). The suppressive effects were similar with different oral estrogen formulations, and the degree of suppression increased with estrogen dosage. In hypogonadal GH-deficient women, oral estrogen treatment also significantly reduced IGFBP-3 and ALS (P = 0.02). The changes in IGF-I in each of the four studies paralleled the changes in both IGFBP-3 and ALS. In conclusion, exogenous estrogens suppress serum IGFBP-3 and ALS in a route- and dose-dependent manner, which are in parallel with the effects on serum IGF-I. These actions of oral estrogen are independent of endogenous GH status.
Kam
G Y
GY
Pituitary Research Unit, Garvan Institute of Medical Research, St. Vincent's Hospital, Sydney, New South Wales, Australia.
Leung
K C
KC
Baxter
R C
RC
Ho
K K
KK
D000279:Administration, Cutaneous; D000284:Administration, Oral; D000368:Aged; D018592:Cross-Over Studies; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D004966:Estrogens, Conjugated (USP) / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D019382:Human Growth Hormone / Q000097:blood*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D046911:Macromolecular Substances; D008875:Middle Aged
D004966:Estrogens, Conjugated (USP); D018972:Insulin-Like Growth Factor Binding Protein 3; D046911:Macromolecular Substances; D019382:Human Growth Hormone; D004997:Ethinyl Estradiol; D004958:Estradiol; D007334:Insulin-Like Growth Factor I