To study the possible role of insulin-like growth factor binding proteins (IGFBPs) in the discrepancy between normal or only slightly retarded growth and substantially reduced concentrations of insulin-like growth factor I (IGF-I) in prepubertal children with insulin-dependent diabetes mellitus (IDDM), we measured the plasma concentrations of IGF-I, IGFBP-1, IGFBP-2 and IGFBP-3 and free insulin in 24 prepubertal diabetic subjects and 12 control children. In addition, the growth hormone response to exercise was evaluated. The diabetic children had significantly decreased peripheral IGF-I levels (8.2 + 1.1 (SEM) vs 16.7 + 2.5 nmol/l; p