PHYSIOLOGICAL HYPERINSULINEMIA ENHANCES COUNTERREGULATORY HORMONE RESPONSES TO HYPOGLYCEMIA IN IDDM

We evaluated the effect of physiologic hyperinsulinemia (plasma insuli n 329 +/- 62 vs 687 +/- 62 pmol/L) on counterregulatory hormone respon ses in 8 IDDM subjects studied during a 2-hour hypoglycemic clamp stud y with an equivalent degree of hypoglycemia (plasma glucose 3.1 +/- 0. 1 and 3.0 +/- 0.1 mmol/L, respectively). Plasma epinephrine levels wer e increased by 71 % during the last 60 minutes of hypoglycemia in the high insulin study (840 +/- 1 80 vs 1440 +/- 31 0 pmol/L, respectively p=0.006). In addition, plasma cortisol and norepinephrine were also i ncreased in the high insulin study (by 19% and 24% respectively, p<0.0 1, for both). Plasma growth hormone and glucagon concentrations were n ot altered by high dose insulin infusion. In spite of increased epinep hrine secretion, the glucose infusion rate required to maintain glucos e was 2-fold greater in the high insulin study, and there was greater suppression of lipolysis in that group. We conclude that hyperinsuline mia may enhance counterregulatory hormone secretion in IDDM.