The effect of thyroid status on the growth hormone response to growth hormone releasing hormone 1-44

The growth hormone (GH) response to iv injection of GH releasing hormone 1-44 (GHRH 1-44) has been examined in 10 hyperthyroid and 6 hypothyroid patients. Both groups of patients were studied at presentation and when euthyroid (mean 5 months for hyperthyroid, 8 months for hypothyroid). Hyperthyroid subjects demonstrated a peak mean (+/- SE) level of 17.7 +/- 3.8 mU/l, with an integrated GH 29.3 +/- 6.4 mU/l.h. When euthyroid the peak mean level was 17.0 +/- 5.0 mU/l and the integrated GH 22.8 +/- 4.2 mU/l.h. Neither change was statistically significant. Hypothyroid subjects had a peak mean level of 5.0 +/- 2.7 mU/l and integrated GH of 5.9 +/- 1.7 mU/l.h and when euthyroid a peak mean level of 7.1 +/- 4.8 mU/l and integrated GH of 8.1 +/- 3.6 mU/l.h. Body weight did not change significantly in this group of hypothyroid subjects with prolonged treatment. The increase in GH response to GHRH previously reported following replacement therapy may reflect a treatment-induced decrease in body weight, or may be a short term effect.