Hypoglycemia

A cross-sectional study by Lupoli et al. (2015) identified GLP-1 as having a role in the hormonal interactions involved in idiopathic reactive hypoglycemia.  They had administered an oral glucose tolerance test to each of their participants; 10 who had been experiencing idiopathic reactive hypoglycemia and 8 healthy controls.  Diabetics and those with other conditions associated with hypoglycemia were excluded from participation.  Four hours into the test, the reactive hypoglycemia participants had significantly lower glucose levels than the control group (43 ±1.6 vs 72 ± 0.3 mg/dL; p = .001), low enough to be a cause of hypoglycemic symptoms. By five hours in these participants had all reached a blood glucose level low enough that symptoms were beginning to appear, whereas no symptoms appeared in the control group.  They were given an infusion of glucose, which resolved their symptoms.  They also had significantly higher insulin at 90 minutes into the test, and significantly lower glucagon at 120-180 minutes.  GLP-1 was twice as high as in the control group.  They did not find insulin sensitivity to be significantly different between the two groups. 

The authors suggest that the increased GLP-1 in response to the oral glucose tolerance test is responsible for the idiopathic reactive hypoglycemia through its ability to both increase insulin and inhibit glucagon.  The elevated insulin and lack of glucagon result in the low blood glucose.  They note the temporal relationship among these changes, with GLP-1 increasing first (at 30 minutes into the test), then insulin increasing at 90 minutes, glucagon going down at 120-180 minutes and finally glucose going down at 240 minutes.  They hypothesize that the elevated GLP-1 could be a result of gastric emptying happening faster than normal.  They express concern that habitual high levels of insulin could eventually lead to diabetes if the pancreatic β-cells become impaired from having to produce so much extra insulin.

Reference:

Lupoli, R., Cotugno, M., Griffo, E., Nosso, G., Riccardi, G., & Capaldo, B. (2015). Role of the Entero-Insular Axis in the Pathogenesis of Idiopathic Reactive Hypoglycemia: A Pilot Study. Journal of Clinical Endocrinology & Metabolism, 100(12), 4441–4446.