Absence of the dawn phenomenon and abnormal lipolysis in Type 1 (insulin-dependent) diabetic patients with chronic growth hormone deficiency

Summary To determine the role of growth hormone in overnight insulin requirements and lipolysis, five patients with chronic growth hormone deficiency and Type 1 (insulin-dependent) diabetes mellitus and six control patients with diabetes were each studied on two separate nights. Insulin was infused at a variable rate throughout one night to maintain euglycaemia and fixed at 04.00 hours on another. During the variable infusion, euglycaemia was maintained in control patients by a 36% increase in insulin infusion rate between 03.00 and 08.00 hours while a 46% decrease in the rate was required in growth hormone deficient patients (p<0.02). Despite this difference, mean free insulin values were equivalent. This finding is suggestive of increased insulin clearance in growth hormone sufficient patients. Glucose levels rose in control and fell in growth hormone deficient patients when insulin infusion rates were fixed at 04.00 hours. Glycerol production and non-esterified fatty acid concentrations were significantly lower in the growth hormone deficient diabetic patients, p<0.001, and when normalized with a heparin infusion, had no effect on insulin requirements. We conclude that: (1) growth hormone contributes to the development of the dawn phenomenon, possibly by increasing insulin clearance (2) growth hormone helps sustain nocturnal lipolysis in Type 1 diabetes and (3) non-esterified fatty acids are not involved in the dawn phenomenon.