Dose-response of prolactin and thyrotropin to N3im-methyl-thyrotropin releasing hormone in euthyroid men

The synthetic N3im-methyl analogue of thyrotropin releasing hormone (methyl-TRH) was administered intravenously to 15 euthyroid men, ages 36-62, in graded doses from 6.25 mug to 500 mug in order to establish the range of response of prolactin (PRL), TSH, T3 and T4 to various doses of methyl-TRH. There was a dose-related rise in serum TSH, PRL, T3, and T4 which gave a nearly linear relationship when the integrated area of response was used as an index of response to the various doses of methyl-TRH. All 15 men had a clear elevation in TSH, PRL, T3 and T4 following the lowest dose of methyl-TRH TESTED (6.25 mug). There was considerable variability in the response to methyl-TRH among the individuals. One hundred mug of methyl-TRH gave a maximum TSH response; a 25 mug dose elicited a maximum PRL response.