Administration of thyrotropin-releasing hormone at weekly intervals results in a diminished thyrotropin response

A diminished thyrotropin (TSH) response to the administration of thyrotropin-releasing hormone (TRH) has been widely reported in depressed patients. Repeated TRH administration at short intervals has been shown to produce a diminished TRH response in healthy subjects. In the present study, TRH (400 micrograms) was administered to ten healthy male subjects at weekly intervals for 4 weeks. The TSH response to TRH diminished steadily from 8.2 +/- 1.3 microU/ml on Trial 1 to 6.3 +/- 0.7 microU/ml on Trial 4 (p less than 0.05). No change in the prolactin response to TRH administration was observed over the four trials. Reduction in the TSH response to TRH was not correlated with basal concentrations of thyroxine, triiodothyronine, or cortisol.