Background: Hypoglycaemic disorders are rare in patients without Diabetes Mellitus but may have a variety of causes including endogenous hyperinsulinaemia (EH). A mixed meal test (MMT) has been proposed as a useful method to confirm the presence of a postprandial hypoglycaemic disorder. However, there are currently no consensus guidelines for interpreting the MMT.
Method: We studied fifty patients who underwent MMT at our hospital between 2008-2016. Patients ingested a standardised breakfast of approximately 1700kJ (48% carbohydrate, 33% fat, 17% protein, 2% other nutrients) after an overnight fast. Venous samples for the measurement of glucose (BG), C-peptide and insulin were collected prior to eating, then every 30 min for five hours. A result was considered positive if venous BG was ≤3.0 mM with the patient experiencing symptoms consistent with hypoglycaemia. We reviewed the indication for testing, the final clinical diagnosis and analysed the glucose and insulin responses to a MMT. We also calculated the Homeostasis Model Assessment (HOMA) score and Matsuda Index (a measure of insulin sensitivity after a glucose load) (1). Results: There were multiple indications for performing a MMT, with the predominant indication being suspicion of EH in otherwise healthy individuals. Three of thirty-six (8.3%) patients who were previously well and referred for suspected EHdeveloped hypoglycaemic during the test. In patients who developed hypoglycaemia, those that were otherwise well had the highest MATSUDA indices, insulin and C-peptide levels, and lower HOMA scores.
Conclusion: We observed different indices of insulin sensitivity according to the underlying cause of postprandial hypoglycaemia. The MMT may be helpful for investigating the presence of a range of post-prandial hypoglycaemic disorders.