Thyrotropin response to thyrotropin-releasing hormone in RDC schizodepressed men

Biological tests may help clarify the relationships of schizoaffective disorder to both major depressive disorder and schizophrenia. Thyrotropin-releasing hormone (TRH), 500 micrograms i.v., was administered to 14 schizodepressed, 23 schizophrenics, 41 unipolar major depressives (all by RDC) and 45 healthy controls, all males 20-67 years old with no significant differences in age, body height or weight. Results showed no differences in maximal delta TSH (dTSH max) amongst schizoaffective depressed, schizophrenia and healthy control groups (10.1 +/- 1.3, 9.2 +/- 1.1, 9.7 +/- 0.8 microU/ml, means +/- SEM respectively). Mean major depressives' dTSH max was lower than in each of the other three groups (6.2 +/- 0.4 microU/ml, P less than 0.01 for all). Utilizing a less than or equal to 5.0 microU/ml cut-off criterion for blunting, the schizodepressed had 36%, schizophrenics 44%, healthy controls 22% and major depressed 59% blunters (P less than 0.05 from other three groups). Schizodepressed patients appeared significantly different from major depressed but closer to schizophrenics (and healthy controls) on the TRH test.