Psychological and thyroid-stimulating hormone changes after thyrotropin-releasing hormone in normal women: antagonism by pretreatment with thyroid hormones.

In a double-blind crossover design we treated 20 normal women with thyrotropin-releasing hormone (TRH), 0.5 mg i.v., and saline in a random sequence. Both injections were preceded, 48 hours before, by a single dose of oral thyroid hormones (TH). TRH caused a shift toward mild euphoria, both on objective and subjective ratings. Although statistically significant, the effect was less than that observed in a previous study of normal women in which TH pretreatment was not used. Thus, TH pretreatment appeared partly to block psychological response to TRH. As expected, TH pretreatment also partly blocked thyroid-stimulating hormone (TSH) responses to TRH. Nevertheless, just as in our previous study, psychological responses were significantly negatively correlated with TSH responses. TH appears to exert two independent negative feedback effects: one on the brain (dimished psychological response); and one on the anterior pituitary (diminished TSH response).