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ELIMINATION OF TRH IN MAN

Institute of Physiology, University of Helsinki Finland.

After injection of 0.2 mg of TRH iv. concentrations of TRH were estimated in plasma, urine and saliva by T₃-TRH bioassay in 5 euthyroid men. Plasma TRH was detectable (over 2 ng/ml) for 15 min and had a half-time of 5 min within the first 5 minutes, Urine TRH level was maximal at 15 min and was about 500-fold that in plasma. Saliva TRH level at 15 min was below 3 ng/ml. The present results are in agreement with those carried out with experimental animals and with ¹²⁵I-TRH, The rapid appearance of TRH in the urine in bioassayable amounts is evidently due to the inability of the kidneys to reabsorb this hormone.

It has previously been reported that injected TRH can be recovered in the urine of the rat in biologically active form (1). In this laboratory it has been shown that ¹²⁵I-TRH behaves similarly in mice (2). This report deals with studies on TRH elimination in man.