THU172 Accuracy Of The Glucagon Testing In The Diagnosis Of Growth Hormone Deficiency During Transition

Disclosure: N. Di Iorgi: None. D. Guglielmi: None. N. Flavia: None. A. Allegri: None. D. Fava: None. E. Casalini: None. G. Patti: None. M. Maghnie: None. Objectives: To evaluate the accuracy of the Glucagon test (GST) compared with the Insulin Tolerance test (ITT) as the gold standard in the diagnosis of Growth Hormone deficiency (GHD) in young adults with childhood-onset GHD (COGHD). Methods: Eighty-six subjects with COGHD (33F, 55M) were evaluated by ITT and GST stimulation tests and IGF-1 SDS at adult height achievement (median age of 17.5; IQR 13.9-18.4 years). Subjects were recruited from a single Center and based on the AACE 2019 Guidelines [1] classified as 1. idiopathic isolated GHD (I-GHD n=40 with normal brain MRI); 2. organic moderate GHD (omGHD with less than 3 pituitary deficiencies-PD and IGF-1<0 SDS, total n=40; n=12 midline defects, n=2 ALL, n=26 CNS tumors); 3. congenital/genetic defects/organic severe GHD (osGHD ≥3 PD and IGF-1 <-2 SDS, total n=6; n=1 midline defect, n=5 CNS tumors). ROC analyses were performed in order to analyze the Sensitivity (Se) and Specificity (Sp) of the GH peak after GST and of IGF-1 SDS compared to ITT. A peak GH value <6μg/L after ITT was suggestive of permanent GHD [2]. Results: Median GH peak to ITT (0.2; IQR 0.01-0.7 μg/L) and GST (0.1; IQR 0.01-1.4μg/L) were lower in osGHD compared to I-GHD subjects (15.0; IQR 8.6-21.9 to ITT and 12.6; IQR 10.5-18.8 μg/L to GST, P’s <0.0001); similarly, GH peak to ITT (2.1; IQR 1.1-6.8 μg/L) and GL (2.7; IQR 1.2-5.8) were lower in omGHD compared to I-GHD subjects (P’s <0.0001). Mean IGF-1 were also lower in osGHD (-3.2 SDS; IQR -7.4- -2.9, P<0.0001) and in omGHD (-2.0 SDS; IQR -2.8 - -0.7; P<0.0001) compared to I-GHD subjects (0,1; IQR -0.6-1.1SDS). A GH peak value to GST of 7.59 mcg/L (Se 92.3%, Sp of 87.2%; AUC=0.94; 95% CI, 0.89-0.99) correctly classified 89.5% of the entire cohort while an IGF-1 cut-off of -1.45 SDS (Se 73%; Sp 93.5%; AUC=0.84; 95% CI, 0.75 - 0.94) correctly classified 83,1%. A GH peak value to GST of 5.81 mcg/L (Se 96.6%, Sp of 81.8%; AUC=0.95; 95% CI, 0.88-1.02) correctly classified 92.5% of omGHD patients while an IGF-1 cut-off of -1.64 SDS (Se 72.3%, Sp of 90.9%; AUC=0.94; 95% CI, 0.89-0.99) correctly classified 77.5% omGHD patients. Median BMI SDS was higher in patients with osGHD (1.8; IQR 1,6- 2.2, P<0.001) and omGHD (0.6; IQR 0.1- 1.8, P<0.001) compared to I-GHD (0.2; IQR -0.7- 1.1). GH peak to GST correlated with BMI SDS only in the total cohort (r -0.313, P=0.0031). Conclusions: Our results suggest that a peak value <6 μg/L after GST is accurate in detecting permanent GHD during transition in a cohort of patients with organic GHD with less than 3 pituitary defects and IGF-1 values <0 SDS; the GH response to GST could be affected by BMI SDS, but further studies are needed. [1] Yuen KCJ et al. Endocr Pract 2019; 25 (11):1191-1232. [2] Maghnie M et al, EJE 2005; 152:589-596. Presentation: Thursday, June 15, 2023