Exercise-induced hyperinsulinism

Exercise-induced hyperinsulinism (EIHI), also known as exercise-induced hyperinsulinemic hypoglycemia, is a rare genetic disorder characterized by inappropriate and excessive insulin secretion triggered by strenuous physical exercise. This condition is caused by activating mutations in the SLC16A1 gene (also known as MCT1), which encodes monocarboxylate transporter 1. Normally, this transporter is not expressed in pancreatic beta cells, but gain-of-function mutations lead to its ectopic expression, allowing pyruvate and lactate generated during exercise to enter beta cells and stimulate insulin release. This results in episodes of hypoglycemia (dangerously low blood sugar) during or shortly after vigorous anaerobic exercise. The primary body system affected is the endocrine/metabolic system, specifically the insulin-regulating function of the pancreas. Key clinical features include recurrent hypoglycemic episodes provoked by exercise, which can manifest as confusion, dizziness, weakness, seizures, and loss of consciousness. Importantly, patients typically do not experience hypoglycemia during fasting or in the absence of exercise, which distinguishes this condition from other forms of congenital hyperinsulinism. Symptoms often become apparent in childhood when children begin engaging in more vigorous physical activities. Management of exercise-induced hyperinsulinism focuses on preventing hypoglycemic episodes. Patients are advised to avoid intense anaerobic exercise or to consume carbohydrate-rich snacks before and during physical activity. Diazoxide, a medication that suppresses insulin secretion, may be used in some cases, though its effectiveness can vary. Unlike some other forms of congenital hyperinsulinism, surgical intervention (pancreatectomy) is generally not required. With appropriate dietary management and activity modification, most patients can lead relatively normal lives, though careful monitoring remains important.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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