Postgastric bypass hyperinsulinemic hypoglycemia syndrome: characterization and response to a modified diet

Some alarming cases of hypoglycemic episodes in patients who have undergone Roux-en-Y gastric bypass have been reported. The syndrome of hyperinsulinemic hypoglycemia with nesidioblastosis after Roux-en-Y gastric bypass has been previously reported and is controversial. It has been suggested that subtotal or total pancreatectomy might be needed to control the symptoms in these patients. We have identified a similar cohort of patients with hyperinsulinemic hypoglycemia for whom we have reviewed patient characteristics and measured the glucose and insulin response to mixed meals.

We reviewed the charts of 14 patients identified by clinic follow-up who reported episodes consistent with hyperinsulinemic hypoglycemia (lightheadedness or loss of consciousness after a high-carbohydrate meal). All patients were given a mixed meal consisting of high carbohydrates on day 1 and a low-carbohydrate meal on day 2. The plasma glucose and serum insulin levels were measured before (fasting) and 30, 60, 90, 120, 150, and 180 minutes after the meal.

After a high-carbohydrate meal, 12 of 14 patients demonstrated hyperglycemia associated with hyperinsulinemia at 30 minutes. These patients subsequently became hypoglycemic while the serum insulin was rapidly declining. After reaching a nadir at 120 minutes, the plasma glucose level corrected spontaneously. After a low-carbohydrate mixed meal, the patients demonstrated very little change in plasma glucose and only a modest increase in serum insulin. Of the 12 patients treated with a low-carbohydrate diet, 6 had substantive symptom improvement, and 10 exhibited at least some improvement.

The hyperinsulinemic hypoglycemia noted in some patients after Roux-en-Y gastric bypass has many similarities to the dumping syndrome. A low-carbohydrate diet successfully improved symptoms in most of our patients. Approaches to treatment should involve a low-carbohydrate diet and alpha-glucosidase inhibitors rather than pancreatectomy.