RESUMO
Acute dexamethasone administration (2 mg/m2 i.v. and 4 mg orally) increases growth hormone (GH) release in children. We evaluated the effect of a low intravenous dose (1 mg/m2) of dexamethasone on GH secretion in 8 short normal children and in 6 GH-deficient children. There was a significant GH increase at 120, 150 and 180 min in short normal children (maximal value: 18.9 +/- 2.1 micrograms/l; mean +/- EP), compared to placebo administration. In contrast, no significant GH elevation was seen in GH-deficient children (1.3 +/- 0.4 micrograms/l). There was no difference in the GH response after intravenous dexamethasone and oral clonidine in these same 8 short normal children and 6 GH-deficient children. Although no significant GH release was observed after dexamethasone or clonidine in GH deficiency, an increase in GH after GH-releasing hormone was seen (6.1 +/- 1.9 micrograms/l). There was a significant GH increase (18.5 +/- 3.3 micrograms/l) after low-dose (2-mg) oral dexamethasone administration in another 8 short normal children, which was similar to values after intravenous injection. No side effects were noted after intravenous or oral dexamethasone. In conclusion, low-dose intravenous or oral dexamethasone administration causes a marked GH release in short normal children, probably mediated by hypothalamic structures.
