Insulin-like growth factor binding protein-1 levels in diabetic adolescents and their relationship to metabolic control.

Circulating levels of the low molecular weight insulin-like growth factor binding protein-1 (IGFBP-1) are insulin dependent and vary markedly throughout the day. IGFBP-1 levels are abnormally high in diabetes but the relationship between this and the metabolic status of the patient has not been defined. We have therefore measured fasting IGFBP-1 levels at 0800 h in 32 diabetic adolescents. IGFBP-1 was measured in 19 of these patients after a normal night and in 27 after a night of euglycaemia, maintained with a glucose clamp. In 13 patients both studies were performed and could be compared. Puberty-matched control data were obtained from 69 normal children. In normal prepubertal children IGFBP-1 levels were high; lower levels were found with advancing pubertal development. This fall in IGFBP-1 correlated with pubertal stage (r= 0.68, p less than 0.001) and with fasting insulin levels (r = 0.60, p less than 0.001) which rose with pubertal advancement. In the diabetic children IGFBP-1 levels also correlated inversely with the 0800 h free insulin level but there was no clear relationship with pubertal development. However, when measured after overnight euglycaemia IGFBP-1 levels correlated inversely with pubertal development (r = 0.67, p less than 0.001) as in the normal children. In the patients studied on two comparable occasions the IGFBP-1 level measured after a normal night relative to that measured under standardized euglycaemic conditions was found to correlate closely with the glycosylated haemoglobin level (r = 0.71, p less than 0.005).