Endocrine Abstracts

The glucagon stimulation test (GST) may be used as a good alternative to the insulin tolerance test (ITT) in the diagnosis of secondary adrenal insufficiency (SAI). The aim of the study was to compare the GST and ITT for diagnostic SAI, to define cortisol cut-off points and factors affecting the appearance of false positive results in young adults followed CSI.

Subjects and Methods: A retrospective study of 28 patients (median age 19 [17; 23]) at least 2 years after CSI because of posterior fossa tumors and 10 healthy volunteers was conducted. ITT and GST were performed within 5–7 days in all patients and voluntaries. Age, sex ratio and BMI were comparable between the groups.

Results: 9/10 healthy had maximum cortisol level (MCL) during ITT more than 540 nmol/l 1 healthy had 440 nmol/l only, therefore 540 nmol/l was chosen as cut-off for ITT. The best cut-off point for diagnosis of SAI by GST was 500 nmol/l (63% sensitivity, 100% specificity). AUC of GST was 93%. 19/28 patients had concordant results of ITT and GST (SAI was confirmed in 9/19 patients). MCL didn’t differ in this groups. 3/28 patients failed ITT (MCL was 421; 471 and 472 nmol/l) but their MCL during ITT was 574, 551 and 660 nmol/l respectively. Therefore, we regarded this result as a false positive ITT. These patients were excluded from the comparison GST and ITT by ROC- analysis. They had statistically significant higher levels of leukocytes (7.44 [5.87; 9.25] vs 5.5 [4.9;6.9], P=0.05), monocytes (0.71 [0.59; 0.75] vs 0.43 [0.36; 0.52], P=0,019), neutrophils (5.11 [3.65; 6.04] vs 2.9 [2.6; 3.7], P=0.019) and lower lymphocytes (24.0% [17.85;25.8] vs 34.9% [28.5; 39.5], P=0.014) levels in comparison with concordant-result patients. 6/28 patients passed ITT and failed GST. They had statistically significant lower levels of leukocytes (5.01[4.04;5.61] vs 6.1 [5.4; 7.3], P=0.012), lymphocytes (1.4 [1.26;1.8] vs 2.3 [1.68; 2.5], P=0.019) and higher levels of cholesterol (5.54 [5.24;6.46] vs 4.9 [4.4; 5.4]), P=0.042) and triglycerides (1.31 [1.07; 1.82] vs 0.94 [0.74;1.5], P=0.05) in comparison with concordant-result patients.

Conclusions: The GST can use as alternative test for the diagnosis of SAI with optimal cut-off 500 nmol/l in young adults followed CSI. The leukocyte formula and lipid changes can lead to false positive ITT and GST results probably. Further prospective studies are required to confirm this data.