High serum levels of growth hormone (GH) and insulin-like growth factor-I (IGF-I) during high-dose GH treatment in short children born small for gestational age.

Context: Epidemiological studies have indicated that high serum levels of GH and IGF-I are associated with long-term risks. Objective: The objective of the study was to evaluate the changes in serum levels of GH during overnight profiles, IGF-I, and IGF binding protein 3 (IGFBP-3) in short small for gestational age (SGA) children during GH treatment with two doses. Patients: Thirty-six prepubertal short SGA children were the subjects of this study. Intervention: Subjects received 1 ( group A) or 2 ( group B) mg GH/m(2).d. Main Outcome Measures: At baseline and after 6 months of GH treatment, overnight GH profiles were performed, and serum IGF-I and IGFBP-3 levels were measured. Results: After 6 months, group B had significantly higher GH levels during the profile ( mean, maximum, and area under the curve above zero line) than group A ( P < 0.009). In group B, maximum GH levels increased from 43.9 - 161 mU/ liter ( P < 0.0002), and in group A, from 57.2 - 104 mU/ liter ( P = 0.002). During the profile (i.e. 12 h per day), children of group B had mean GH levels of 64.4 vs. 34.8 mU/ liter in group A ( P = 0.001). The IGF-I and IGF-I to IGFBP-3 ratio SD scores increased significantly in both groups, but were higher in group B than A [1.5 vs. 0.2 ( P = 0.002) and 1.4 vs. 0.3 ( P = 0.007), respectively]. In group B, 74% of the children had IGF-I levels in the highest quintile during GH treatment compared with 19% in group A. Conclusion: Our study shows that high-dose GH treatment in short SGA children results in high serum GH and IGF-I levels in most children. We recommend monitoring IGF-I levels during GH therapy to ensure that these remain within the normal range.