Prepro-TRH is a regulator of the biosynthesis of TSH in the anterior pituitary gland and acts as a neurotransmitter and neuromodulator in the central and peripheral nervous systems. A non-TRH fragment of the prepro-TRH, the connecting peptide PS4 (prepro-TRH 160-169), is able to potentiate the TRH-induced TSH release in a dose-dependent manner.Rat: H-Ser-Phe-Pro-Trp-Met-Glu-Ser-Asp-Val-Thr-OH or H-SFPWMESDVT-OH