Thyrotropin-Releasing Hormone (TRH), Free Acid (TRH-OH), induces various thyroidal and non-thyroidal effects, most notably the feedback regulation of thyroid hormone levels.

Thyrotropin-releasing-hormone (TRH) stimulated the release of newly synthesized GH and PRL, but not thyroid-stimulating hormone. In addition, TRH stimulated a dose-related increase in the release of newly synthesized GH and PRL at 10(-9) to 10(-7) M. Cyclo(His-Pro) stimulated the release of newly synthesized GH dose- dependently. TRH, cyclo(His-Pro), and hGHRH stimulated GH synthesis, while SRIF inhibited this at 10(-7) M. The release of newly synthesized PRL into culture medium was also stimulated by TRH and hGHRH, but inhibited by SRIF. PRL synthesis was not affected by TRH-OH and cyclo(His-Pro). Intracellular contents of GH and PRL in the pituitary did not change significantly.TRH plays an important role in both GH and PRL synthesis and release[1].