LONG-TERM EFFECTS OF INSULIN-LIKE GROWTH-FACTOR (IGF)-I TREATMENT ON SERUM IGFS AND IGF BINDING-PROTEINS IN ADOLESCENT PATIENTS WITH GROWTH-HORMONE RECEPTOR DEFICIENCY

OBJECTIVE The aim of this investigation was to study the effect of rel atively high dose IGF-I therapy given for several months, on serum lev els of IGF-I, IGF-II and IGFBP-3, and on IGF-I pharmacokinetics in pat ients with growth hormone insensitivity due to on receptor dysfunction . DESIGN AND PATIENTS Two adolescent subjects from Ecuador were treate d with recombinant IGF-I at a dosage of 120 mu g/kg s.c. twice daily, in combination with a GnRH analogue for 8 months. MEASUREMENTS Serum w as sampled at baseline and at 3-8 months, for determination of IGF-I, IGF-II and IGFBP-3 by radioimmunoassay, and for evaluation of IGFBPs a nd IGFBP-3 protease activity by Western ligand blot and protease assay , respectively. RESULTS Peak serum IGF-I levels ranged from 272 to 492 mu g/l. Mean serum IGF-II levels were decreased concurrently with the increase in IGF-I. Serum IGFBP-3 levels failed to rise with prolonged IGF-I treatment. There was no apparent change in the half-life of IGF -I during the treatment period. CONCLUSIONS IGF-I administration does not increase serum levels of IGFBP-3 or significantly alter IGF-I phar macokinetics.