ENHANCED PLASMA GH RESPONSES TO SIMULTANEOUS ADMINISTRATION OF TRH AND GHRH IN PATIENTS WITH PRIMARY HYPOTHYROIDISM

The mechanism of aberrant GH responses to TRH was indirectly evaluated in 7 patients with primary hypothyroidism. All patients showed GH res ponse to TRH. When TRH was administered together with GHRH, the plasma GH response was much greater than after a single administration of TR H or GHRH (TRH+GHRH vs. TRH or GHRH: max. Delta GH, 16.4 +/- 3.2 vs. 5 .4 +/- 1.3 or 6.0 +/- 0.8 mu g/L; AUC, 1282.7 +/- 234.7 vs. 384.0 +/- 95.0 or 441.8 +/- 66.2, both P<0.01). The combined administration of T RH and GHRH caused an additive, but not a synergistic, GH response. In contrast, 8 normal subjects showed neither any plasma GH response to TRH nor enhancement by TRH of GHRH-induced GH response following combi ned administration. It is concluded that the sites of action of TRH se emed to be different from GHRH in patients with primary hypothyroidism .