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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

Abstract:

Objective. The aim of this investigation was to study the effect of relatively high dose IGF-I therapy given for several months, on serum levels of IGF-I, IGF-II and IGFBP-3, and on IGF-I pharmacokinetics in patients with growth hormone insensitivity due to GH receptor dysfunction. Design and patients. Two adolescent subjects from Ecuador were treated with recombinant IGF-I at a dosage of 120 μg/kg s.c. twice daily, in combination with a GnRH analogue for 8 months. Measurements. Serum was 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 and IGFBP-3 protease activity by Western ligand blot and protease assay, respectively. Results. Peak serum IGF-I levels ranged from 272 to 492 μg/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 administration does not increase serum levels of IGFBP-3 or significantly alter IGF-I pharmacokinetics.