Physicians monitoring patients who have undergone gastric bypass surgery should be on the alert for a new, potentially dangerous hypoglycemia (low blood glucose) complication that, while rare, may require quick treatment, according to a new study by collaborating researchers at Joslin Diabetes Center, Beth Israel Deaconess Medical Center (BIDMC), and Brigham and Women's Hospital (BWH) and published in the October issue of the journal Diabetologia.
The paper follows on the heels of a Mayo Clinic report on six similar case studies published in July in the New England Journal of Medicine. About 160,000 people undergo gastric bypass surgery every year.
The study details the history of three patients, who did not have diabetes, who suffered such severe hypoglycemia following meals that they became confused and sometimes blacked out, in two cases causing automobile collisions. The immediate cause of hypoglycemia was exceptionally high levels of insulin following meals. All three patients in the collaborative study failed to respond to medication, and ultimately required partial or complete removal of the pancreas, the major source of insulin, to prevent dangerous declines in blood glucose.
"Severe hypoglycemia is a complication of gastric bypass surgery, and should be considered if the patient has symptoms such as confusion, lightheadedness, rapid heart rate, shaking, sweating, excessive hunger, bad headaches in the morning or bad nightmares," says Mary-Elizabeth Patti, M.D., Investigator in Joslin's Research Section on Cellular and Molecular Physiology and Assistant Professor of Medicine at Harvard Medical School. "If these symptoms don't respond to simple changes in diet, such as restricting intake of simple carbohydrates, patients should be evaluated hormonally, quickly," she adds. Dr. Patti and Allison B. Goldfine, M.D., also an Investigator at Joslin and Assistant Professor of Medicine at Harvard Medical School, were co-investigators of the study.
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.