Insulin-like growth factor-I and IGF binding protein-3 remain high after GnRH analogue therapy in girls with central precocious puberty.
OBJECTIVE
IGF-I rises in normal adolescence and in central precocious puberty (CPP), secondary to a rise in sex steroids and GH. The aim of this study was to examine changes in serum IGF-I and its major binding protein IGFBP-3 after pharmacological arrest of puberty.


METHODS
Ten girls diagnosed for CPP were evaluated before and during the first 3 months of GnRH analogue (GnRHa) therapy aimed at suppression of the gonadal axis. Serum IGF-I was measured by immunoradiometric assay (IRMA) and IGFBP-3 by both IRMA and Western ligand blotting (WLB).


RESULTS
Serum IGF-I was markedly higher in patients with CPP as compared with age matched controls (48.8 +/- 6.5 vs 23.1 +/- 4.9 nmol/l, P < 0.01). While GnRHa therapy caused serum oestradiol levels to return to prepubertal levels in all 10 patients, serum IGF-I levels decreased only minimally after 1, 2 or 3 months of therapy (43.2 +/- 5.6, 42.3 +/- 6.4 and 44.1 +/- 7.2 nmol/l respectively). Serum IGFBP-3 levels as determined using IRMA were also higher in CPP compared with age matched controls (4.70 +/- 0.37 vs 3.71 +/- 0.42 mg/l, P < 0.01). These differences were also evident when measured by WLB. GnRHa therapy caused a small and insignificant decrease in serum IGFBP-3 levels after 1, 2 or 3 months of therapy (4.57 +/- 0.33, 4.48 +/- 0.4 and 4.42 +/- 0.3 mg/l respectively).


CONCLUSIONS
The lack of suppression of both IGF-I and IGFBP-3, despite therapy which halts puberty and slows growth velocity, suggests that steroids may be involved in the induction of changes in the GH/IGF-I axis but not in their subsequent maintenance.
Kanety
H
H
Institute of Endocrinology, Chaim Sheba Medical Center, Tel Hashomer, Israel.
Karasik
A
A
Pariente
C
C
Kauschansky
A
A
D015153:Blotting, Western; D002648:Child; D017373:Cyproterone Acetate / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D004958:Estradiol / Q000097:blood; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000627:therapeutic use; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D011629:Puberty, Precocious / Q000097:blood* / Q000188:drug therapy*; D017329:Triptorelin Pamoate
D018972:Insulin-Like Growth Factor Binding Protein 3; D017329:Triptorelin Pamoate; D007987:Gonadotropin-Releasing Hormone; D017373:Cyproterone Acetate; D004958:Estradiol; D007334:Insulin-Like Growth Factor I