Hypoglycaemia following physical exercise in a patient with novel SLC16A1 variant

Rare defects in the promoter region of SLC16A1, the gene encoding monocarboxylate transporter 1 (MCT-1), result in exercise-induced hyperinsulinism. In this disorder, inappropriate insulin secretion is triggered by anaerobic exercise with consequent hypoglycaemia. We describe the case of a 41-year-old man presenting with a generalised tonic-clonic seizure and severe hypoglycaemia following strenuous exercise. A subsequent prolonged fast with incorporation of exercise into the protocol demonstrated hyperinsulinaemic hypoglycaemia; genetic testing revealed a variant of unknown significance in the SLC16A1 gene. Administration of subcutaneous octreotide resulted in dose-dependent reduction in hyperinsulinaemia and hypoglycaemia.