Plasma Epinephrine and Norepinephrine Levels During Insulin-Induced Hypoglycemia in Man*†

Plasma epinephrine and norepinephrine concentrations were measured by the ethylenediamine technic before and during hypoglycemia in 11 patients undergoing insulin-coma therapy. In 6 studies carried out during the first week of treatment, plasma epinephrine levels increased from a mean value of 0.2 μg. per liter (control) to 1.4 μg. per liter following administration of insulin. In 9 studies carried out during the second and third weeks of therapy, the control values were significantly elevated (0.9 μg. per liter), although peak epinephrine concentrations reached after insulin were similar to those observed during the first week. In 9 studies performed in patients treated for more than three weeks, the control epinephrine concentration was 0.15 μg. per liter and no significant increase was observed during hypoglycemia. Norepinephrine levels remained unchanged in the 2½-hour period following administration of insulin in these subjects. However, a significant increase was noted in samples obtained between two and a half hours and four hours after insulin. The results of these studies indicate that the adrenal medullary response to hypoglycemia in man is associated with a rise in plasma epinephrine levels as measured by the ethylenediamine technic, and that this response is significantly altered by repeated insulin induced hypoglycemia.