The study sample will include 160 adults, ages 55-90, half of whom will be cognitively healthy normal adults and half of whom will meet diagnostic criteria for Mild Cognitive Impairment (MCI). Each of these groups will contain equal numbers of men and women. The treatment with GHRH will be twenty weeks in duration. In light of the documented interactions between estrogens and GHRH/GH/IGF-I, each of the two study arms will contain equal proportions of women not on estrogen replacement therapy (NERT) and women on oral estrogen replacement therapy (ERT). ERT women will maintain a regular steady dosage of estrogens for at least seven days preceding each assessment