Short and long term effects of growth hormone on circulating levels of insulin-like growth factor-I (IGF-I), IGF-binding protein-1, and insulin: a placebo-controlled study

Abstract

The short and long term effects of GH on serum concentrations of insulin-like growth factor-I (IGF-I), IGF-binding protein-1 (IGFBP-1), and insulin were investigated in women participating in an in vitro fertilization program. In this placebo-controlled study, sterile saline (eight women) or 24 IU GH (eight women) were given im on alternate days, starting on cycle day 4, in combination with GnRH and human menopausal gonadotropin. IGFBP-1 levels decreased significantly during the first 4 h after GH administration, whereas no significant changes were seen in the placebo group. The concentrations of serum IGF-I and insulin did not change during 4 h after GH injection. During the 11-day follow-up period, serum levels of both IGF-I and insulin were significantly higher in GH-treated than in placebo-treated women. These results suggest that the serum concentration of IGFBP-1 is not completely GH independent. They also support the earlier findings that long term treatment with GH increases serum IGF-I and insulin levels.