Contrasting metabolic effects of continuous and pulsatile growth hormone administration in young adults with type 1 (insulin-dependent) diabetes mellitus.

Plasma growth hormone profiles in adolescents with Type 1 (insulin-dependent) diabetes mellitus are characterized by both increases in pulse amplitude and higher baseline concentrations. To determine which of these abnormalities adversely affect metabolic control, we studied six young adults overnight on three occasions. On each night somatostatin (50-100 micrograms.m2-1.h-1) and glucagon (1 ng.kg-1.min-1) were infused continuously and 18 mU/kg of growth hormone was given as either: three discrete pulses of 6 mU.kg-1.h-1 at 180-min intervals or a 12-h infusion (1.5 mU.kg-1.h-1) or buffer solution only on a control night. Euglycaemia was maintained by an insulin-varying clamp. Blood samples were taken every 15 min for glucose and growth hormone and every hour for intermediate metabolites and non-esterified fatty acids. Comparable normoglycaemic conditions were achieved on all three nights. Growth hormone levels achieved (mean +/- SEM) on study nights were: 32.8 +/- 2.2 mU/l (peak level during growth hormone pulses); 9.8 +/- 0.8 mU/l (continuous growth hormone) and 1.1 +/- 0.3 mU/l (control level). Pulsatile growth hormone administration led to an increase in insulin requirements (mean +/- SEM: 0.17 +/- 0.03 vs control 0.09 +/- 0.01 mU.kg-1.min-1, p less than 0.05) whereas insulin requirements following continuous growth hormone administration were unchanged. Cross-correlation confirmed an increase in insulin requirements occurring 135 min after a growth hormone pulse (r = 0.21, p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)