Growth hormone response to L-Dopa in diabetes mellitus

Summary The effect of a single oral dose of 0.5 g L-Dopa on the serum levels of human growth hormone (HGH) was studied in 38 diabetics and 15 age and sex matched control subjects. The diabetics were divided into three clinical sub-groups:a) juvenile diabetics, 15;b) maturity onset diabetics, 15; andc) insulin dependent diabetics admitted in a state of ketoacidosis, 8. L-Dopa-induced HGH secretion in juvenile and maturity onset diabetics was studied before and after the control of diabetes mellitus. HGH was estimated by a homologous double antibody radioimmunoassay. The fasting serum HGH in maturity onset diabetics did not differ significantly from that of control subjects; it was significantly higher in juvenile diabetics and in ketotic diabetics during ketosis and after the control of diabetes. In juvenile diabetics the mean fasting serum HGH level decreased after the control of diabetes but was still significantly higher than in normal subjects. L-Dopa caused a significant rise in serum HGH in 14 control subjects. Among the diabetics the HGH response to L-Dopa was either absent or markedly attenuated in the uncontrolled state. After the control of diabetes a significant improvement in HGH response to L-Dopa was evident in juvenile diabetics but no improvement was seen in maturity onset diabetics. There is thus a considerable derangement in HGH secretion in diabetes mellitus. The various possibilities are discussed.