In conclusion, we expanded the number of patients with newly diagnosed GH-producing pituitary adenomas who had been evaluated with TRH to examine the paradoxical response and concluded that, unlike the previously published data [10, 16], the relationship between the GH response to TRH and tumor volume did not demonstrate any evidence for the inverse correlation; ΔGHmax-min during the TST but not basal GH, IGF-I levels, and tumor volume showed significant differences according to responsiveness to TRH and tumor volume. The gene discussed is IGF1; the disease is pituitary gland adenoma.