Abstract 87: A comparative study to validate peak growth hormone levels in clonidine and glucagon stimulation test in severe short stature

Introduction: Severe short stature is defined as a height standard deviation score (SDS) of less than −3 below the mean for chronological age and sex. Growth hormone deficiency (GHD) is one of the most important causes of short stature. The diagnosis of GHD is classically established after two provocative tests in patients with short stature. Only three growth hormone (GH) provocative agents like insulin, clonidine, and glucagon are available in India. The insulin tolerance test (ITT), although considered agold standard test, is infrequently used nowadays as it poses several risks. Clonidine stimulation test (CST) is the most performed stimulation test due to being easily available and less cumbersome. The glucagon stimulation test (GST), offers several advantages over other tests, in view ofmultiple sample requirements, it has been poorly studied to date in India. In this study, weanalyzedthe diagnostic efficacy of GST andCST in suspected GHD cohorts and compared the peak GH level between these tests. Materials and Methods: The study was conducted in 3000 bedded multi-specialty tertiary care center, in South Tamil Nadu between 2020 and 2022. Based on the auxological criteria, 33 patients of severe short stature with suspected GHD were included in this cross-sectional study after IEC approval. They were subjected to CST and GST on two different weeks according to standard protocols. Blood samples were collected for GH at 0, 30, 60, 90 and 120 minutesfollowing clonidine stimulation and 0, 30, 60, 90, 120, 150 and 180 minutesafter Glucagon stimulation. GH assay was performed by using electrochemiluminescence (ECLIA - Roche Diagnostics - Cobas e411 analyzer). A Peak GH level of less than 8 ng/ml is considered diagnostic of GHD. All procedures were carried out inthe early morning after an overnight fast. Patients of peripubertal age were primed with Estradiol valerate for 3 days before performing the tests. Results: Among 33 patients,18 were males and 15 were females. The mean chronological age was 11.5 ± 4.1 years. The mean height SDS, weight SDS and target height SDSwere-4.22 ± 1.2, -3.55 ± 1.14, and -1.45 ± 0.95 respectively. Among 33 patients, 27 patients were diagnosed withGHD, and 6 patients with Idiopathic short stature (ISS). The mean peak GH level during CST and GST in diagnosing GHD were 2.0015 ± 0.718 (Range 0.17 – 6.4 ng/ml) and 1.244 ± 0.442 (Range 0.16 – 5.3 ng/ml) respectively. Whereas mean peak GH levels with CST and GST in patients with ISS were 16.3233 ± 7.579 (Range 11.3 – 23.9 ng/ml) and 12.7717 ± 2.812 (Range 11.0 – 14.7 ng/ml) respectively. The sensitivity and specificity of CST was 100.00% (87.23% to 100.00%), 90% (52.1 to 92.2%) respectively. Whereas sensitivity and specificity of GST were 100.00%(80.49% to 100.00%), and 100%(54.07% to 100.00%). Results of both CST and GST were concordant in 30 (91%) patients whereas discordant in 3 (9%) patients. The number and percentage of peak GH levelsnoted with CST at 0 min, 60 min, and 90 minwere 3 (9.1%), 10 (30.3%), and 20 (60.6%) respectively. No peak GH level was noted at 30 min, and 120 min during CST. The number and percentageof peak GH levels with GST at0 min, 120 min, and 180 min were 3 (9.1%), 14 (42.4%), and 16 (48.5%) respectively. No peak GH level occurredat 30, 60, 90 and 150 min during GST. MRI showed normal pituitary, hypoplastic pituitary, and pituitary stalk interruption syndrome in 10 (30%), 13 (40%), and 10 (30%) of patients respectively. Conclusions: The utility of both CST and GST was comparable in diagnosing short stature with severe GHD. However, CST performs better than GST inassessing the severity of GH deficiency in these patients. Our study concluded that the number and timing of blood sampling can be minimized into three following both CST (0, 60, 90 minutes) as well as GST (0, 120, 180 min) without sacrificing accuracy.