Exercise-Induced Hyperinsulinism

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2021-01-23
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Exercise-induced hyperinsulinism (EIHI) is a form of diazoxide-sensitive diffuse hyperinsulinism (DHI) characterized by episodes of hypoglycemia induced by exercise due to an inappropriate lactate and pyruvate sensitivity in pancreatic beta-cells.

Epidemiology

Prevalence is estimated at 1/50,000 live births for CHI, EIHI accounts for a very small portion of this group.

Clinical description

EIHI patients present recurring episodes of hypoglycemia associated with elevated insulin levels, within 30 minutes of a short period of anaerobic exercise. This response may be mimicked by the injection of pyruvate. The degree of hypoglycemia associated with exercise is variable and is only partially responsive to diazoxide.

Etiology

Mutations in the promoter element of SLC16A1 (SLC16A1, 1p12, solute carrier family 16, member 1) leads to an inappropriate presence of monocarboxylic acid transporter 1(MCT1) . MCT1 allows lactate and pyruvate to enter mitochondria and the respiratory chain to produce ATP. SLC16A1 expression is normally suppressed in pancreatic beta-cells, impeding the glucose metabolites lactate and pyruvate from inducing an inappropriate insulin secretion in response to their plasma level increase during physical exertion

Genetic counseling

Mutations of the promoter region of SLC16A1 that permit gene expression in pancreatic beta-cells identified to date are dominant.