Plasma corticotropin-releasing factor in depressed patients before and after the dexamethasone suppression test

Background: Plasma cortisol, β-endorphin, corticotropin, corticotropin-releasing factor, and salivary cortisol concentrations, resting and after ingestion of 1 mg of dexamethasone, were investigated in depressed patients and controls. Methods: Fourteen outpatients from the psychiatric department diagnosed with depressive disorder (ICD-10 Classification) participated in the study. The comparison group consisted of 12 healthy volunteers from the hospital staff. All hormones were measured using direct iodine-125 radioimmunoassay, except corticotropin-releasing factor, which included a sample preextraction and concentration step. Results: The basal plasma cortisol and corticotropin-releasing factor levels in depressive disorder were significantly higher than in the healthy group. After dexamethasone administration, corticotropin-releasing factor plasma values decreased significantly in the depressed group, but showed no significant changes in the controls. In depressive disorder baseline values correlated significantly for salivary cortisol and plasma cortisol, salivary cortisol and plasma corticotropin-releasing factor and plasma corticotropin and β-endorphin. Similar correlations were found in the healthy subjects, except for salivary cortisol and plasma corticotropin-releasing factor. Conclusions: These findings indicate that the increased corticotropin-releasing factor plasma concentrations demonstrated in depressive disorder reflect the hypothalamic corticotropin-releasing factor hypersecretion evidenced in this illness. Therefore, measurements of plasma corticotropin-releasing factor levels can be considered a reliable tool for investigating the role of this peptide in the pathophysiology of depression.