HYPOGLYCEMIA COUNTERREGULATION IN ELDERLY HUMANS - RELATIONSHIP TO GLUCOSE-LEVELS

This study was designed to define the effect of human aging on hypogly cemia counterregulatory mechanisms. A hyperinsulinemic (2 mU.kg(-1).mi n(-1)) glucose clamp procedure was used to control glucose and insulin levels during stepwise lowering of plasma glucose. Counterregulatory hormones, hepatic glucose production (HGP), glucose utilization, and s ymptoms of hypoglycemia were studied in 13 healthy young [age 24 +/- 1 (SE) yr] and 11 healthy old (age 65 +/- 1 yr) nondiabetic volunteers on two occasions: 1) at matched euglycemia and 70 and 60 mg/dl (study 1) and 2) at matched euglycemia ana 60 and 50 mg/dl (study 2). The old had consistently lower epinephrine (P < 0.005), glucagon (P < 0.02), cortisol (P < 0.05), and pancreatic polypeptide (P < 0.02) responses a t the 60-mg/dl glucose step in study 1. However, these differences wer e no longer detectable at the more severe hypoglycemic stimulus of 50 mg/dl in study 2. A consistent increase in HGP occurred in both groups only at the 50-mg/dl glucose step (study 2) and was not different bet ween young and old. There were also no differences in symptom response s between young and old. In summary, we found that elderly individuals have a subtle impairment of the glucose counterregulatory response du ring moderate hypoglycemia, but this impairment is no longer detectabl e during more severe hypoglycemia.