Combined clonidine-short-ACTH test for the simultaneous assessment of growth hormone reserve and hypothalamic-pituitary-adrenal axis integrity in children.

OBJECTIVE To determine the feasibility of using the combined oral clonidine and the short-ACTH test instead of the sometimes dangerous insulin-induced hypoglycemia test as a screening procedure, for the simultaneous assessment of growth hormone reserve and hypothalamic-pituitary-adrenal axis integrity in children with growth retardation. DESIGN Evaluative study. METHOD Seventy-three children (52 males) aged 11+/-3 years with attenuated growth (group 1) were tested by combined clonidine (150 microg/m(2)) and short-ACTH test (either the standard 250 microg or the low-dose 1 microg/1. 73 m(2)). Thirty-one children received no pretreatment (nonprimed) (subgroup 1NP), and 42 were primed with ethynylestradiol 40 microg/m(2)/day two days before testing (subgroup 1P). The control group for the short-ACTH test (group 2) consisted of 42 children and adolescents (13 males) aged 12+/-3 years with early or accelerated puberty or premature closure of epiphyses, who received ACTH only (21 standard, 21 low-dose) with no evidence of adrenal or pituitary pathology. The peak GH response was compared between the primed and the nonprimed group 1 subjects, and the cortisol levels were compared between the combined test subgroups and the controls. The peak pass level for growth hormone was 10 ng/ml; the peak pass level for cortisol was 520 nmol/l. RESULTS Sixty-four of the 73 children in group 1 (87.7%) showed a growth hormone level of >/=10 ng/ml on the first stimulation test, including 26/31 (84%) nonprimed and 38/42 (90.5%) primed. Of the 9 patients who failed the first clonidine test, 4 also failed the second, primed test, including 1/5 nonprimed patients (20%) and 3/4 primed patients (75%). This yielded a GH deficiency/insufficiency rate of 5.5% and a rather low false-positive rate of 13.3% (4/30) for the nonprimed subjects and 2. 6% (1/39) for the primed subjects. Peak 30-min cortisol in response to ACTH stimulation was similar in the patients who underwent the 250 microg or the 1 microg test within each group (subgroup 1NP, subgroup 1P and group 2); therefore, the results for the two tests were considered together. Compared with group 2, subgroup 1NP patients had a similar 30-min cortisol response (P=NS), and subgroup 1P patients had a much higher response (P<0.05) (group 2=690+/-145 nmol/l, subgroup 1NP=772+/-195 nmol/l, subgroup 1P=934+/-209 nmol/l). However, there was no significant difference in the increment in cortisol response between the three groups. CONCLUSIONS Our results suggest that the combined clonidine-short-ACTH test is a reliable and safe tool for the simultaneous assessment of growth hormone reserve and hypothalamic-pituitary-adrenal axis integrity in children.