<h4>Context</h4>The glucagon stimulation test (GST) is increasingly used as an alternative to the insulin tolerance test for diagnosing persistent GH deficiency (GHD) during transition, though its accuracy and appropriate cutoff values are still uncertain.<h4>Objective</h4>To investigate the GH response to GST in transitional-age patients with childhood-onset GHD (CO-GHD), with a focus on the influence of body mass index (BMI) and the underlying etiology.<h4>Patients and methods</h4>A total of 180 patients with CO-GHD (median age 17.39 years) underwent GST. The gene discussed is INS; the disease is Onset.