Hyperinsulinemic Hypoglycemia in a Patient With a Mutation in the Insulin Receptor

Hyperinsulinemic hypoglycemias resulting from variants in the insulin receptor (INSR) gene are rare but clinically important disorders. We present a male patient in his 30s, experiencing recurrent postprandial hypoglycemic events. Endocrine evaluation revealed an elevated insulin-to-C-peptide ratio. A hypoglycemia gene panel, using next-generation sequencing, identified a heterozygous nonsense variant in the INSR gene (NM_000208.4) c.3079C > T, p.(Arg1027*). Initial treatment with diazoxide reduced hypoglycemic symptoms and led to weight loss and decreased hemoglobin A1c due to reduced compensatory carbohydrate intake. However, limiting side effects on diazoxide prompted a treatment switch to lanreotide with maintained absence of hypoglycemic events. This case highlights the importance of considering variants in the INSR gene as a differential diagnosis in hyperinsulinemic hypoglycemia cases, even in adults.