ESPE Abstracts

Background: Glucagon stimulation test (GST) is used to assess growth hormone (GH) and cortisol reserves in children being investigated for GH deficiency, as a small percentage of children with idiopathic GH deficiency can also exhibit deficiency in the adrenocorticotrophic hormone (ACTH)-cortisol axis. However, the extent of normal cortisol response after glucagon stimulation and its associations with clinical and laboratory parameters have not been thoroughly studied.

Aim: To assess total cortisol levels in children being evaluating for short stature with normal cortisol reserve and to correlate this response to clinical and laboratory data.

Patients and Methods: During the last 5 years, children assessed with glucagon test in our department were recruited retrospectively. Inclusion criteria were: i)age > 1 year, ii)absence of chronic illness or medication interfering with ACTH-cortisol axis, iii)GH stimulation levels > 3ng/mL at least in one provocation test (glucagon or clonidine), iv)absence of multiple pituitary growth hormone deficiencies, v)normal short Synacthen test in cases of low cortisol response in glucagon test. Glucagon tests were performed after an overnight fasting with the intramuscular administration of glucagon (0.03 mg/kg, max: 1mg). Blood samples were drawn with 30 minutes intervals until 180 minutes for the assessment of GH, total cortisol and glucose levels and the calculation of area under the curve (AUC).

Results: Two hundred and thirty-seven subjects (160 males, 67,5%) were finally included in the analysis. Mean age at the time of the evaluation was 9.02 ± 3.19 years (range: 1.86 – 16.45 years). Cortisol peak levels but not cortisol AUC were significantly increased in females compared to males (26.83 ± 7.31 µg/dL versus 24.04 ± 7.20 µg/dL). When linear correlations were studied, both cortisol peak levels and cortisol AUC were linearly but inversely correlated to age (r=-0.234, P<0.001 and r=-0.315, P<0.001, respectively). Finally, cortisol AUC was inversely correlated to weight Z-scores (r=-0.160, P=0.014).

When our analysis was limited only to subjects with intact GH response (GH peak > 7ng/ml), age was still inversely correlated to cortisol AUC (r=-0.312, P<0.001), and cortisol AUC was linearly correlated to GH AUC assessed with clonidine test (r=0.223, P=0.013).

Conclusions: Girls and younger children seems to exhibit higher cortisol response to glucagon test, whereas younger and leaner subjects show also greater cortisol response. In subjects with intact GH reserve, a greater cortisol response in glucagon test was linearly correlated with a greater GH response in clonidine but not in glucagon test.