The glucagon stimulation test in comparison to the insulin tolerance test to diagnose growth hormone deficiency and central adrenal insufficiency in patients following craniospinal irradiation in young ages

Aims: The insulin tolerance test (ITT) is the “gold standard“ in the diagnosis of growth hormone (GH) deficiency (GHD) and central adrenal insufficiency (CAI) but it is rather difficult to perform, has a sufficient number of contraindications, need hospitalization. The glucagon stimulation test (GST) may be used as alternative method because it can be carry out as an outpatient and it has fewer contraindications. The aim of this study was to compare the GST and ITT for diagnostic GDH and CAI in patients following craniospinal irradiation (CSI) in young ages. Methods: Examined 5 girls and 6 boys with posterior fossa tumors in history. They received treatment, including total or partial resection of the tumor, chemotherapy, CSI 35 Gy for whole brain, 55 Gy for tumor area and 32 Gy for spine. Median age at the time of treatment was 12 years [9;15], median follow-up was 5 years [3;7]. All patients ITT and GST had conducted. Severe GHD was diagnosed when GH < 3 ng/ml, CAI – when plasma cortisol < 550 nmol/l. Results: According to results 8/11 patients diagnosed severe GHD (median GH = 0.83 ng/ml [0.5 – 1.3]) and in the ITT 10/11 patients revealed GHD (median GH = 0.809 ng/ml [0.37 – 1.85]). 9/11 patients had CAI in GST (median peak plasma cortisol = 375 nmol/l [342;475]). But the diagnosis was refuted in 4/9 patients in ITT, peak plasma cortisol was > 550 nmol/ml (Me 625 nmol/l [607 – 887]). Conclusions: Surprisingly GST turned out more sensible in GHD diagnosis than ITT. The obtained results allow us to recommend GST as initial outpatient test. If patient have peak GH < 3 ng/ml and peak cortisol < 550 nmol/ml in GST, ITT is required. Because the sample is small GST can't substitute ITT now. The study continues.