Since centrally released GHRH controls the whole GHRH-GH-IGF-I axis, a novel and very potent antagonist of GHRH (designated MIA-690), synthesized in our laboratory, was tested in vivo and in vitro in different models of Alzheimer's disease to clarify the effects of GHRH on the progress of symptoms and to elucidate the mechanism of action. The gene discussed is GHRH; the disease is early-onset autosomal dominant Alzheimer disease.