The effect of estrogen level on glucose-induced changes in serum insulin-like growth factor binding protein-1 concentration.
OBJECTIVE
To investigate the regulation of insulin-like growth factor binding protein-1 (IGFBP-1) concentration during ovarian stimulation.


METHODS
A prospective study of patients undergoing in vitro fertilization treatment.


METHODS
Infertility unit at the University Central Hospital of Oulu, a tertiary referral center.


METHODS
Sixteen healthy, regularly menstruating lean tubal infertility patients.


METHODS
Oral glucose tolerance test was performed first in a hypoestrogenic state after suppression by long-term gonadotropin-releasing hormone (GnRH) agonist and, second, in a hyperestrogenic state after stimulation by human menopausal gonadotropins.


METHODS
Serum concentrations of IGFBP-1, insulin-like growth factor I (IGF-I), insulin and sex hormone-binding globulin were measured before and 2 hours after glucose administration.


RESULTS
Before and after glucose administration, the serum IGFBP-1 concentrations were significantly higher in the hyperestrogenic state (estradiol [E2] level 3.5 +/- 0.57 nmol/L) after ovarian stimulation than in the GnRH-analogue-induced hypoestrogenic state before the gonadotropin treatment (E2 level 0.10 +/- 0.02 nmol/L). On both occasions glucose-induced hyperinsulinemia caused a significant decrease in the circulating IGFBP-1 levels, whereas the IGF-I levels remained unchanged. There was a significant correlation between E2 and the insulin-suppressed IGFBP-1 level. The sum of follicular diameters correlated positively with the serum IGFBP-1 concentration.


CONCLUSIONS
Gonadotropin-induced hyperestrogenism is related to elevated serum IGFBP-1 levels, either via estrogen-stimulated synthesis or via increased contribution from multiple follicles. Glucose-induced hyperinsulinemia suppresses serum IBFBP-1 concentration equally both in the hypoestrogenic and hyperestrogenic states. Because of similar IGF-I levels, it is likely that the biological activity of IGF-I is different before and after gonadotropin stimulations.
Martikainen
H
H
Department of Obstetrics and Gynecology, University of Oulu, Finland.
Koistinen
R
R
Seppälä
M
M
D000328:Adult; D002064:Buserelin; D002352:Carrier Proteins / Q000097:blood*; D004958:Estradiol / Q000097:blood*; D005260:Female; D005307:Fertilization in Vitro; D005947:Glucose / Q000494:pharmacology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008596:Menotropins; D011446:Prospective Studies; D012738:Sex Hormone-Binding Globulin / Q000378:metabolism
D002352:Carrier Proteins; D007328:Insulin; D018970:Insulin-Like Growth Factor Binding Protein 1; D012738:Sex Hormone-Binding Globulin; D004958:Estradiol; D008596:Menotropins; D007334:Insulin-Like Growth Factor I; D005947:Glucose; D002064:Buserelin