Growth hormone response to hyperinsulinaemia in insulin-dependent diabetics. Comparison of patients with and without retinopathy.

Growth hormone levels were measured in glucose clamp studies on 13 insulin-dependent diabetic patients with retinopathy and 9 age, sex, and weight matched patients without retinopathy. Four non-diabetic subjects were used as controls. The glucose was kept constant at 12 +/- 0.85 mmol/l (mean +/- S.D.) in the diabetic groups, and at 6 mmol/l in the non-diabetic controls. Insulin was infused at sequential rates of 0.3, 1.0, and 10 mU/kg/min. Basal levels of growth hormone were not significantly different in those with and without retinopathy (5.7 +/- 4.9, 9.4 +/- 10.6 mU/l p = 0.21). Growth hormone levels were compared in each group during a 60 minute steady state period for each insulin infusion rate. At all 3 infusion rates, the diabetics with retinopathy produced a rise in growth hormone, while the non-diabetics did not (1.24 +/- 0.6 mU/l). The patients with retinopathy produced more growth hormone than those without at each infusion rate (12.2 +/- 11.5 vs. 2.8 +/- 5.1, p = 0.03; 10.6 +/- 11.1 vs. 1.6 +/- 1.7, p = 0.02; 19.7 +/- 20.6 vs. 4.2 +/- 4.8, p = 0.03). These data confirm that insulin alone can stimulate growth hormone secretion in insulin-dependent diabetics with retinopathy. Evidence is provided indicating that patients with retinopathy produce more growth hormone than those without.