Serum levels of IGFBP-3: usefulness in diagnosis of GH deficiency and relationship to measurements of GH secretion in children.

Aims of the study were to assess the relationship between serum levels of IGFBP-3 with IGF-I serum levels, peak GH levels in response to two stimulation tests (PKGH) and GH urinary excretion in children, and to examine the usefulness of IGFBP-3 for diagnosis of GH deficiency. Our study group consisted of 86 children with normal stature, 12 children with normal short stature and 12 children with GHD. In all children, serum levels of IGF-I and IGFBP-3 were measured and GH urinary excretion was assessed in overnight urine collections. Children with short stature had two stimulation tests and the peak GH level was used in the analysis. IGFBP-3 SDS was strongly correlated with IGF-I SDS (r = 0.63, p < 0.001), significantly correlated with peak GH (r = 0.42, p < 0.05) and weakly, but not significantly, correlated with urinary GH excretion. Among the 12 children with GHD, only two had normal IGFBP-3 values (sensitivity 83%). In contrast, all normal short children except one had IGFBP-3 levels within the normal range, defined by the 5th and 95th percentile (specificity 92%). Sensitivity and specificity of IGF-I were respectively 67% and 50%. In conclusion, IGFBP-3 levels are strongly correlated with IGF-I levels, weakly correlated with peak GH response to provocative tests and may serve as a valuable parameter, in combination with others, in the evaluation of the GH-IGF axis.