Pancreatic alpha-cell function in idiopathic reactive hypoglycemia

Area of Science:

• Endocrinology
• Metabolic Disorders
• Gastroenterology

Background:

• Idiopathic reactive hypoglycemia (IRH) is often overdiagnosed, with known issues in insulin secretion and sensitivity.
• Data on glucagon secretion in IRH is limited, hindering a full understanding of the syndrome.
• Understanding hormonal responses is crucial for accurate diagnosis and management of postprandial hypoglycemia.

Purpose of the Study:

• To investigate and compare glucagon and insulin responses in individuals with IRH versus normal subjects.
• To assess hormonal reactions to a standard oral glucose tolerance test (OGTT) and a protein meal.
• To explore the role of glucagon secretion abnormalities in the pathophysiology of IRH.

Main Methods:

• A randomized crossover study comparing five IRH subjects and six normal controls.
• Administered a 100g oral glucose tolerance test (OGTT) and a 100g protein meal in separate sessions.
• Measured plasma glucose, insulin, and glucagon levels at baseline and timed intervals post-ingestion.

Main Results:

• IRH subjects exhibited significantly higher basal glucagon levels compared to normal subjects.
• During OGTT, IRH subjects showed impaired glucose tolerance, delayed insulin peaks, and a failure of glucagon to increase during hypoglycemia.
• Protein meal ingestion led to a greater glucose decline in IRH subjects, accompanied by a significantly blunted glucagon response compared to controls.

Conclusions:

• Basal hyperglucagonemia in IRH may indicate glucagon receptor hyposensitivity.
• Altered glucagon secretion, including lack of suppression during hyperglycemia and blunted response to protein, is evident in IRH.
• Glucagon receptor downregulation and impaired sensitivity/secretion likely contribute to postprandial hypoglycemia in IRH.