Endocrine Abstracts

Objective: To investigate the insulin response during a 5 hour Oral Glucose tolerance test (OGTT) in subjects with and without symptoms of reactive hypoglycaemia.

Methods: 12 patients with suspected reactive hypoglycaemia were studied. After fasting from midnight, they were given a 75 g glucose drink at 9 am the following morning. Plasma glucose and insulin levels were measured at baseline and at 30 minute intervals for 5 hours. Relative insulin increase, shape of insulin response curve, time difference in peak insulin and glucose and basal insulin sensitivity using the HOMA method were measured.

Results: Patients with reactive hypoglycaemia were defined as those with symptoms of hypoglycaemia and a blood glucose ≤3.5 mmol/l. 7 of the 12 patients were confirmed to have reactive hypoglycaemia. The other 5 patients were asymptomatic and had glucose levels ≥ 3.6. All patients with reactive hypoglycaemia had a peak of insulin ≥ 5 times basal concentration while patients without had peak insulin ≤ 5 times basal. For patients in both groups, peak insulin concentration coincided with peak glucose. Patients without reactive hypoglycaemia had a peak insulin response at 30 minutes. Those with reactive hypoglycaemia appeared to have lost their first phase insulin response with a more gradual increase in insulin concentration and a peak insulin level at 60 minutes. HOMA values showed that the patients with reactive hypoglycaemia were more insulin sensitive than those without.

Conclusions: Patients with reactive hypoglycaemia are more insulin sensitive and have an abnormal insulin response to an oral glucose challenge with a more gradual increase and delayed peak in insulin concentration. In patients where the diagnosis of reactive hypoglycaemia is not clear, an insulin level at 60 minutes ≥ 5 times baseline may help confirm the diagnosis.