Growth hormone (GH) has acute actions to stimulate lipolysis and ketogenesis after 2 to 3 hours, effects that may be important in the adaptation to stress and fasting. This is accompanied by a decrease in insulin sensitivity in both liver and muscle. These combined effects may be very deleterious to insulin-dependent diabetic patients, in whom increased GH secretion may precipitate and maintain acute metabolic derangement (ketoacidosis) and be a major initiator of the dawn phenomenon. On the other hand, augmented GH secretion plays a beneficial role in the defense against hypoglycemia, in particular during prolonged hypoglycemia and in patients with impaired ability to secrete other counterregulatory hormones appropriately. It is also certain that GH is a potent anabolic hormone in terms of promoted nitrogen retention, but the extent to which these well-known actions are direct or secondary to hyperinsulinemia, increased activity of insulin-like growth factors (IGFs), or release of protein-conserving lipid intermediates has eluded precise characterization.