During his first week of life, a diagnostic fasting test revealed hypoglycemia following only 3.5 hr of fasting (plasma glucose 35 mg/dl, 2.0 mmol/l) with suppressed beta‐hydroxybutyrate and an inappropriately large glycemic response to glucagon (delta 82 mg/dl), confirming HI. This evidence concerns the gene GCG and Hypoglycemia.