Mechanisms of Post-Bariatric Hypoglycemia

A CGM sensor (Dexcom G4 or other professional version available at onset of study) will be placed during visit 1 in blinded (masked) mode, and will be worn for 10 days. Data will be analyzed to determine patterns of glucose during both day and night intervals.

The activity monitor (Fitbit Charge 2) will be worn by participants for 10 days to assess activity, concurrent with CGM sensor wear.

After an overnight fast, participants will be given a standard liquid mixed meal; blood samples will be collected at baseline (fasting) and at defined time points after a meal for metabolic and hormonal analyses.

After baseline blood sampling, glucagon will be administered by injection, and blood samples will be collected for analysis of glucose and hormone responses. This will allow us to assess whether sensitivity to glucagon is altered in PBH.

This test will assess hormonal responses to hypoglycemia. Participants will arrive after an overnight fast. After baseline blood sampling, an infusion of insulin and glucose will be started, and infusions will be adjusted to allow glucose levels to drop very gradually. Blood samples will be collected for measurement of hormonal responses to lowering of glucose. This test will allow us to determine whether secretion of hormones which counteract hypoglycemia (counterregulatory hormones) is reduced in patients with PBH as compared with other groups.

Participants will be asked to provide a fecal sample, collected at home, which will be analyzed to determine the types of bacteria present in the feces.