The risk of post-load hypoglycemia one year after bariatric surgery increased by 28% with every 10 ng/ml increment of pre-operative IGF-1 serum concentration (OR 1.28; 95%CI: 1.03–1.55; p = 0.0297) and by 18% with post-operative IGF-1 concentrations (OR 1.18; 95%CI: 1.03–1.33; p = 0.0155). The gene discussed is IGF1; the disease is Hypoglycemia.