Plasma growth hormone response to oral clonidine as compared to insulin hypoglycemia in obese children and adolescents.

Abstract

The response of plasma growth hormone (hGH) to a single oral dose of clonidine (0.15 mg/m2) was compared with that obtained with insulin hypoglycemia (ITT) induced by administration of double the usual dose (0.2 U/kg i.v.) in 13 obese subjects aged 5-17 years (7 males, 6 females) with a subscapular skinfold greater than 20 mm and a weight greater than 2 SD of the median. Six healthy subjects (3 males, 3 females), aged 8-14 years who served as controls received the usual dose of 0.1 U/kg i.v. in the ITT. Clonidine induced an increase of more than 10 ng/ml in the plasma hGH levels in 10 (4 males, 6 females) of the 13 obese subjects and in all of the healthy controls, with peak levels ranging from 14.3 to 31.0 ng/ml (m +/- SD 21.0 +/- 5.2 ng/ml); the ITT elicited a similar rise in only 6 of the 13 subjects and 3 of the healthy controls, with peak levels ranging from 9.8 to 20.0 ng/ml (m +/- SD 14.4 +/- 4.5 ng/ml). Clonidine decreased plasma insulin levels in all the obese female subjects (by a mean of 65%) whereas in the obese males the insulin pattern was variable. There was no change in blood glucose levels following the administration of clonidine; during the ITT all subjects showed a decrease to less than 50 mg/dl. Blood pressure decreased by a mean of 20 mmHg during the clonidine test. This study demonstrates that clonidine is a more effective hGH stimulus than insulin induced hypoglycemia in normal and in obese children and that the lower hGH secretion of the obese is confirmed by the clonidine test.