Suppression by thyrotropin-releasing hormone (TRH) of human growth hormone release induced by L-dopa.
Oral administration of L-dopa (600 mg) significantly raised plasma human growth hormone (hGH) in 6 of 7 normal subjects examined. This L-dopa induced hGH release was significantly suppressed by the intravenous infusion of 1 mg of thyrotropin-releasing hormone (TRH). TRH administration alone had no significant effect on plasma hGH. In contrast, plasma human prolactin (hPRL) consistently increased following TRH infusion. L-dopa significantly lowered basal plasma hPRL levels and also significantly blunted TRH-induced hPRL release. These results suggest that TRH plays an inhibitory role in the regulation of hGH secretion in normal subjects, whereas it stimulates hPRL release.
D000284:Administration, Oral; D003864:Depression, Chemical; D013006:Growth Hormone / Q000097:blood*; D007275:Injections, Intravenous; D007980:Levodopa / Q000008:administration & dosage / Q000494:pharmacology*; D013973:Thyrotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
D007980:Levodopa; D013973:Thyrotropin-Releasing Hormone; D013006:Growth Hormone