Utility of the Glucagon Stimulation Test for the Diagnosis of Adult Growth Hormone Deficiency

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SAT 109-133-GHRH, GH & IGF Biology & Signaling
Bench to Bedside
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-116
Jessica R Wilson*, Jessica K Devin, Vipul T Lakhani and Andrea L Utz
Vanderbilt University Medical Center, Nashville, TN
Background: The use of the glucagon stimulation test (GST) for the diagnosis of adult growth hormone (GH) deficiency (GHD) is becoming increasingly common due to the unavailability of GH releasing hormone and given limitations and patient intolerance of the insulin tolerance test. Few studies have characterized the utility of GST among patients with a high pre-test probability of GHD. The goal of this retrospective study was to investigate the relationship between GH and blood glucose (BG) dynamics following GST and to determine the impact of gender, baseline glycemic status, body mass index (BMI), age and oral estrogen use on peak GH level. We secondarily provide data on the safety and tolerability of GST and recommended test length.

Methods: We studied all patients who underwent GST at Vanderbilt University Medical Center from September 2009 to September 2011. Patients were selected for GST based on history and clinical findings. Comparisons of continuous variables between groups were analyzed using the Mann-Whitney U-test. Spearman correlation was used to determine an association between continuous variables. Results are presented as mean ± standard deviation unless otherwise noted. All data analyses were performed using IBM SPSS Statistics (v. 20).

Results: 26 patients (N=17; 65.4% female) underwent GST and had sufficient laboratory data available for analysis. Mean BMI was 36.4 ± 9.1 kg/m2. Five females (29.4%) were taking an oral estrogen at the time of testing. Six patients (23.1%) had a baseline fasting BG >100 mg/dL on the morning of testing (including 2 with a known diagnosis of diabetes mellitus). The change in BG following GST was not associated with change in GH. While patients with a baseline BG >100 mg/dL had a higher peak BG (187.5 ± 43.3 vs 144.2 ± 24.3; p=0.039) and higher nadir BG (87.0 ± 30.7 vs 60.1 ± 8.5; p=0.013), their peak GH did not significantly differ (p=0.929). Females had a higher peak GH than men (mean 4.4 ± 4.2 vs. 0.8 ± 0.7; p=0.013), and females taking oral estrogen had a higher peak GH than those not taking estrogen (8.2 ± 4.6 vs. 2.8 ± 2.9; p=0.014). There was no linear relationship between peak GH and age or BMI. Mean time of peak GH was 125.8 min ± 68.4 (range 0-210 minutes). Inclusion of GH data beyond 180 minutes did not influence the diagnosis of GHD using a cut-off of 3 ng/dl. There were no serious adverse events. Three patients reported nausea. 

Conclusions: Our findings do not demonstrate an association between GH and BG dynamics following GST. Glycemic status at the time of testing did not affect peak GH. Females had a significantly higher GH peak, which may be related to oral estrogen use. The GST was well tolerated, and a testing period of 3 hours is safe and sufficient for the diagnosis of GHD.

Nothing to Disclose: JRW, JKD, VTL, ALU

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