5-Hydroxytryptophan-induced cortisol response and CSF 5-HIAA in depressed patients.

To determine if the enhanced cortisol response to oral administration of the serotonin (5-HT) precursor 5-hydroxytryptophan (5-HTP) that has been reported in unmedicated depressed and manic patients might be related to brain monoaminergic metabolism, the authors assessed correlations between 5-HTP-induced cortisol response and CSF in nine depressed patients. They found a significant negative correlation with CSF levels of 5-hydroxyindoleacetic acid, a 5-HT metabolite, but not with CSF levels of other monoamine metabolites. This finding is consistent with the hypothesis that low presynaptic brain serotonergic activity may be related to enhanced cortisol response to 5-HTP in depressed patients.