The inhibitory action of the pineal extract on TRH.

The effects of a single dose and of 5 doses (5 days) of a bovine polypeptide pineal extract (PE) on the pituitary TSH reserves and on the blood level of thyroid hormones were studied on hypothyroid patients. The blood levels of PBI, total T4 (radiocompetitive), free T4, T3 and TSH (RIA) in basal conditions and during the TRH test (i.v. administration of 200 mug TRH), In the presence and absence of the treatment with PE were determined. Thirty minutes following i.m. administration of PE a decrease was noticed in the high level of the basal TSH in all the patients as well as maintenance or even exaggeration of the TRH response. After 5 days of PE administration a decrease was noticed in the basal TSH, with preservation of a strong response of the TSH release after TRH administration. In these patients a slight decrease was observed in PBI, total and free T4 and T3, when their initial level was close to normal. The results show the results show the intervention of the pineal extract by inhibiting the endogenous TRH.