Elevation of immunoreactive CSF TRH in depressed patients.

The concentration of thyrotropin-releasing hormone (TRH), a tripeptide (pyroglutamylhistidylprolin-amide), in the CSF of drug-free patients with DSM-III major depression, somatization disorder, and peripheral neurological disorders was measured with a sensitive and specific radioimmunoassay. The depressed patients had markedly higher CSF TRH concentrations than the other patient groups, and this finding could not be attributed to any demographic variables. The elevation of TRH in CSF provides further evidence of hypothalamic-pituitary-thyroid dysfunction in depression.