TRH stimulation test and depression.

A thyrotropin-releasing hormone (TRH) stimulation test was performed in 52 male inpatients with major depressive disorder. Twenty-nine percent of the 52 subjects had a delta thyroid-stimulating hormone (delta TSH) less than 5 microU/ml. The cerebrospinal fluid (CSF) amine metabolites, 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5HIAA), were measured in 29 subjects, and a dexamethasone suppression test (DST) was performed in 48 subjects. Of the three CSF amine metabolites, only MHPG correlated significantly with baseline TSH and none correlated with delta TSH. The baseline TSH correlated positively with the TSH response at 30 minutes. Neither baseline TSH nor delta TSH correlated with cortisol levels before or after dexamethasone. The correlation between CSF MHPG and serum TSH suggests a relationship between central norepinephrine and baseline TSH.