Bioactive insulin-like growth factor (IGF) I and IGF-binding protein-1 in anorexia nervosa.

Abstract

Regulation of IGF-I activity appears crucial in anorexia nervosa (AN) during adaptation to chronic starvation as well as during the regenerative processes on nutritional restoration. The objective of this study was to examine the relationship between IGF-I bioactivity and IGF-binding capacity as expressed as formation of the binary complex of IGF-binding protein-1 (IGFBP-1) and IGF-I in patients with AN at different stages and with different subtypes of the disease. This was a longitudinal study. The study took place at a clinical research center at a university hospital. We studied a total of 45 women with AN and 24 age-comparable healthy controls. IGF-I bioactivity was determined using an IGF-I receptor activation assay, and IGF-I/IGFBP-1 complex formation was determined by an assay that allows direct determination of the binary complex. IGF-I bioactivity was significantly decreased in serum from patients with AN. We found significant correlations between total, ultrafiltered free, and bioactive IGF-I. Despite increased IGFBP-1 concentrations, levels of IGF-I/IGFBP-1 binary complex were not significantly increased in AN. Oral contraceptives were associated with increased levels of IGF-I, IGFBP-1, and binary complex formation. Ghrelin levels were only significantly raised in those patients who had lost more than 5% of the body weight during the last 4 wk, whereas ghrelin levels in weight-stable as well as in weight-gaining patients did not significantly differ from the controls. Total IGF-I level is a suitable marker of IGF-I bioactivity in emaciated patients with AN irrespective of the clinical subtype and acute nutritional state.