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Bariatric Surgery Can Mask Diabetes

Dec 10, 2010

Bariatric surgery may appear to cure diabetes based on measurements such as fasting plasma glucose and A1c but postprandial glucose may tell a different story….

According to Anna Marina, MD, and Dace Trence, MD, of the University of Washington in Seattle, in a case report a patient who had had bariatric surgery achieved fasting blood sugar and HbA1c results that allowed him to stop taking insulin, but he frequently had postprandial blood sugar scores above 200 mg/dL.

“Fasting blood glucose and HbA1c are insufficient criteria to establish remission of diabetes after surgery,” Marina said. “Glucose tolerance tests or continuous glucose monitoring should be considered to provide a better assessment of glycemic status in this group of patients.”

Bariatric surgery has increasingly been championed as a cure for Type 2 diabetes, potentially through improvement in insulin resistance and secretion. Fasting plasma glucose and HbA1c often provide evidence of that conclusion. But, Marina said, while these results certainly improve diabetes outcomes, they shouldn’t yet be called a cure.

She bases her conclusions on a case report of a 55-year-old patient with a body mass index (BMI) of about 45 kg/m2 who’d had Roux-en-Y gastric bypass surgery. He’d previously had a seven-year history of diabetes.

After surgery, the patient’s insulin requirements dropped from 100 units to 30 units daily. At four months, he’d lost more than 100 pounds, and his HbA1c and fasting plasma glucose were markedly improved — falling from 9 to 6.1%, and into the normal 90 to 150 mg/dL range, respectively. At that point, he no longer needed insulin.

At seven months after surgery, the patient’s HbA1c was 6.2%, and his fasting glucose was normal, but he had sporadic postprandial glucose of 180 mg/dL.

Subsequent three-day continuous glucose monitoring revealed spikes in postprandial blood glucose above 200 mg/dL, peaking at 294 mg/dL. The researchers gave him repaglinide to lower his postprandial hyperglycemia.

The findings are consistent with the results of a larger study by Roslin et al, which looked at 38 patients more than six months after Roux-en-Y gastric bypass surgery. Six patients had diabetes before surgery, and five of them thought their disease had been cured until glucose tolerance testing proved otherwise.

The researchers also cited flaws in the 621 studies involved in a meta-analysis by Buchwald et al, which concluded that bariatric surgery was a cure for diabetes. They said most of the studies were retrospective, single-armed, and made up of relatively young women. Also, only 1.6% of them provided Class I evidence.

Marina concluded that HbA1c and fasting blood glucose measurements aren’t sufficient criteria to establish a “curing” of Type 2 diabetes after gastric bypass surgery. Rather, postprandial blood glucose or continuous glucose monitoring should be considered in order to “provide a clear assessment of glycemic status specific to gastric bypass surgery effects in those with established Type 2 diabetes.”

Arthur Chernoff, MD, chair of endocrinology at Albert Einstein Medical Center in Philadelphia, said the results are feasible, as it’s challenging to decide at which point the patient indeed has diabetes.

“It doesn’t surprise me that some patients [who’ve had bariatric surgery] will have high blood sugar because I don’t think that the procedure cures whatever it is that’s causing diabetes in the first place,” said Chernoff, who wasn’t involved in the study.

Practice Pearl:
  • Explain that fasting blood sugar and HbA1c results after bariatric surgery may be inadequate for detecting diabetes, as postprandial blood glucose may tell a different story.

Marina AL, Trence DL “Is diabetes mellitus really cured by gastric bypass surgery?” AACE 2010; Abstract 210 Authors and Disclosures