In summary, despite the obvious experimental differences between human GH-secreting adenomas and the GC tumors, we believe that our observations warrant the use of the GC tumor bearing rats as an animal model to study GH-secreting adenomas, the deleterious effects caused by prolonged exposure to elevated circulating GH/IGF-I levels as well as the phenotypic changes that occur after normalization of the circulating GH/IGF-I levels by surgical or phamarcological treatment. The gene discussed is IGF1; the disease is adenoma.