Oral dexamethasone administration: new pharmacological test for the assessment of growth hormone secretion.
Acute intravenous (i.v.) dexamethasone administration has been described recently as a new test for the diagnosis of growth hormone (GH) deficiency. In the present study, a new protocol of dexamethasone administration was evaluated. Twelve normal adults and 18 normal prepubertal children were studied. The dexamethasone i.v. test was performed in six adults at a dose of 4 mg and 12 children at a dose of 2 mg/m2. Blood samples were collected 15 min before, at time zero and every 15 or 30 min during 5 h, resulting in a total of 16 samples. In the remaining six adults and six children, 8 and 4 mg, respectively, of dexamethasone were administered orally at the subject's home, and blood sampling started 90 min later when they arrived at the hospital. Plasma GH was measured by radioimmunoassay. The dexamethasone-induced GH response (mean +/- SEM, micrograms/l) to the i.v. or oral protocol did not differ in either the adults (i.v. 8.2 +/- 2.1; oral 8.0 +/- 1.6) or the children (i.v. 14.9 +/- 1.3; oral 13.6 +/- 1.8). It is concluded that the simpler protocol of acute oral dexamethasone administration hereby presented can be a safe and suitable test of GH secretion.