Abnormal glucose tolerance testing following gastric bypass demonstrates reactive hypoglycemia

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Abstract
Symptoms of reactive hypoglycemia have been reported by patients after Roux-en-Y gastric bypass (RYGB) surgery who experience maladaptive eating behavior and weight regain. A 4-h glucose tolerance test (GTT) was used to assess the incidence and extent of hypoglycemia. Thirty-six patients who were at least 6 months postoperative from RYGB were administered a 4-h GTT with measurement of insulin levels. Mean age was 49.4 ± 11.4 years, mean preoperative body mass index (BMI) was 48.8 ± 6.6 kg/m2, percent excess BMI lost (%EBL) was 62.6 ± 21.6%, mean weight change from nadir weight was 8.2 ± 8.6 kg, and mean follow-up time was 40.5 ± 26.7 months. Twelve patients had diabetes preoperatively. Thirty-two of 36 patients (89%) had abnormal GTT. Six patients (17%) were identified as diabetic based on GTT. All six of these patients were diabetic preoperatively. Twenty-six patients (72%) had evidence of reactive hypoglycemia at 2 h post glucose load. Within this cohort of 26 patients, 14 had maximum to minimum glucose ratio (MMGR) > 3:1, 5 with a ratio > 4:1. Eleven patients had weight regain greater than 10% of initial weight loss (range 4.9–25.6 kg). Ten of these 11 patients (91%) with weight recidivism showed reactive hypoglycemia. Abnormal GTT is a common finding post RYGB. Persistence of diabetes was noted in 50% of patients with diabetes preoperatively. Amongst the nondiabetic patients, reactive hypoglycemia was found to be more common and pronounced than expected. Absence of abnormally high insulin levels does not support nesidioblastosis as an etiology of this hypoglycemia. More than 50% of patients with reactive hypoglycemia had significantly exaggerated MMGR. We believe this may be due to the nonphysiologic transit of food to the small intestine due to lack of a pyloric valve after RYGB. This reactive hypoglycemia may contribute to maladaptive eating behaviors leading to weight regain long term. Our data suggest that GTT is an important part of post-RYGB follow-up and should be incorporated into the routine postoperative screening protocol. Further studies on the impact of pylorus preservation are necessary.

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