A revised interpretation of the TRH test results in female depressed patients. Part II: Prolactin responses. Relationships with sex hormones, corticosteroid state, age, monoamines and amino acid levels.

Prolactin (PRL) levels were recorded in baseline conditions and 20 and 60 min after thyrotropin releasing hormone (TRH) administration (200 micrograms i.v.) in 60 depressed females categorized according to DSM-III. Peak PRL responses were significantly (r = 0.727, P less than 0.001) correlated with their baseline levels. Consequently, the PRL responses to TRH were largely predicted by baseline PRL levels. It was suggested that the PRL responses to TRH consisted of two parts. The first component was a relative exaggeration of basal PRL, reflecting the basal activity of the hormone. The second component was the residual response. This part was estimated by partialling out the relative effects of basal PRL on peak PRL responses by means of regression analysis. Basal PRL and residual PRL responses were uninformative for major depression. Post-menopausal females showed significantly reduced basal PRL levels. There was a significant negative correlation between basal PRL and follicle stimulating hormone levels, age and post-dexamethasone cortisol values. The residual PRL responses were negatively correlated with free triiodothyronine levels and positively with serotonergic variables, i.e., 5-hydroxyindoleacetic acid in 24-h urine and the ratio L-tryptophan/competing amino acids.