Insulin-like growth factor-I (IGF-I) serum concentrations in depressed patients: relationship to saliva cortisol and changes during antidepressant treatment.

INTRODUCTION: The present study was designed to test the hypothesis that total and free insulin-like growth factor-I (IGF-I) serum concentrations in depressed patients are related to hypothalamus-pituitary-adrenal (HPA) system activity and show a longitudinal decline in patients responding to treatment as well as to declining HPA system activity. METHODS: We measured total and free IGF-I as well as IGF-binding protein-3 in 77 depressed patients after wash-out of pre-medication and again after 28 or 35 days of treatment with paroxetine or amitriptyline. RESULTS: Total but not free IGF-I serum concentrations are related to saliva cortisol concentrations in drug-free depressed patients. In responders to both amitriptyline and paroxetine, total IGF-I serum concentrations declined during treatment. DISCUSSION: Our findings show IGF-I to be related to HPA system activity and to decline in responders to treatment while serum concentrations of the biologically active free IGF-I are neither related to HPA system activity nor do they change during the course of treatment. Our data do not support the hypothesis that free IGF-I may play a major role in physical disturbances in depressed patients.