The study reported on three patients a woman in her 20s, another in her 60s and a man in his 40s. All three lost significant amounts of weight through gastric bypass surgery, putting them in the normal Body Mass Index (BMI) range. Each, however, developed postprandial hypoglycemia (low blood glucose after meals) that failed to respond to dietary or medical intervention. As a result, all patients required removal of part or all of the pancreas. In all three cases, it was found that the insulin-producing islet cells in their pancreases had proliferated abnormally.
A potential cause of this severe hypoglycemia in these patients is "dumping syndrome," a constellation of symptoms including palpitations, lightheadedness, abdominal cramping and diarrhea, explains Dr. Patti. Dumping syndrome occurs when the small intestine fills too quickly with undigested food from the stomach, as can happen following gastric bypass surgery. But the failure to respond to dietary and medical therapy, and the conditions worsening over time suggested that additional pathology was needed to explain the symptoms' severity, Dr. Patti adds. "The magnitude of the problem was way beyond what doctors typically call dumping syndrome," she says.
Other causes of postprandial hypoglycemia can include overactive islet cells, sometimes caused by excess numbers of cells, a tumor in the pancreas that produces too much insulin, or familial hyperinsulinism (hereditary production of too much insulin), which in severe cases can necessitate removal of the pancreas.
In patients following bariatric surgery, additional mechanisms may contribute to overproduction of insulin. "First, insulin sensitivity (responsiveness to insulin) improves after weight loss of any kind, and can be quite significant after successful gastric surgery," says Dr. Patti. "Second, weight gain and obesity are associated with increased numbers of insulin producing cells in the pancreas, and so som
Contact: Marjorie Dwyer
Joslin Diabetes Center