November 01, 2010
4 min read

Post-gastric bypass hypoglycemia: A serious complication of bariatric surgery

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Obesity is a rapidly increasing problem in the United States and worldwide, with more than 30% of adult Americans now affected. Unfortunately, we are lacking in effective therapies to promote significant weight loss.

Although aggressive lifestyle modification is highly effective, it is plagued by difficulties with poor compliance, access and reimbursement. Medical therapy for obesity has limited efficacy and significant side effects, and with the recent withdrawal of sibutramine from the US market, there are limited options (See more info on this here). Therefore, more patients and providers are turning to bariatric surgery for the treatment of obesity and its comorbidities. Especially in the case of Roux-en-Y gastric bypass surgery, this is a highly effective therapy that can lead to significant weight loss and also improve metabolic parameters independent of weight loss.

Roux-en-Y gastric bypass surgery involves attaching a small pouch of the upper stomach to the early part of the jejunum, thereby bypassing the majority of the stomach and the duodenum. This results in an increased sense of fullness and reduction in appetite, as well as alterations in hormonal release from the small intestine in response to food. This procedure has been found to lead to resolution of type 2 diabetes in up to 80% of patients. It has therefore been proposed as a potential “cure” for type 2 diabetes.

Evaluating risks of surgery

Dawn Belt Davis

As with any therapy, Roux-en-Y gastric bypass surgery can result in adverse effects and complications. Although the immediate risks of morbidity and mortality from the surgery are low, the long-term risks associated with malabsorption and other complications are still being clarified as an increasing number of patients are undergoing this procedure.

One long-term risk is the development of postprandial hypoglycemia. This phenomenon was first described in the literature in 2005. The prevalence still remains unknown, but as endocrinologists we will undoubtedly be seeing more of these patients. Hypoglycemia typically does not present until 2 to 3 years after gastric bypass surgery. These hypoglycemic episodes are characterized by low blood sugars that occur 2 to 3 hours after a meal. Fasting hypoglycemia is typically not seen. The etiology seems to be excessive insulin secretion in response to the meal. It is well documented that patients are more insulin sensitive after gastric bypass surgery, but the pathophysiology of these specific patients who develop hypoglycemia remains unclear. It is hypothesized that it may be related to elevations in the incretin hormones glucagon-like peptide 1 and gastric inhibitory polypeptide, and their ability to stimulate additional insulin secretion. It has also been debated whether increased beta-cell mass may lead to excessive insulin secretion.

Unfortunately, the effect of this disorder on the lives of patients can be devastating and severe. They become trapped in a vicious cycle in which the very treatment of their hypoglycemia leads to yet another episode a few hours later. Hypoglycemic unawareness can develop relatively rapidly, as these patients may have several episodes per day. Patients can have loss of consciousness and seizures, which may result in motor vehicle accidents. Many patients go undiagnosed for extended periods of time, as there is limited awareness of this disorder in the medical community and the initial episodes are often mild with subtle symptoms.

There are limited resources to determine the appropriate treatment strategy for these patients, with most studies reporting only a small number of cases.

First-line treatment should be educating the patient to follow a diet with strict avoidance of high-glycemic-index carbohydrates and limited portions of any carbohydrate. In addition, acarbose (Precose, Bayer Pharmaceuticals) is often successful in patients with relatively mild disease to reduce carbohydrate absorption. In patients who do not respond to these initial therapies, the addition of medications to antagonize insulin activity or minimize insulin secretion can be helpful. Calcium-channel blockers, octreotide or diazoxide are other options that can be tried. In the most severe patients, partial pancreatectomy has been performed; unfortunately, it has not been universally successful at reversing the hypoglycemic episodes. It is unknown if reversal of the gastric bypass is a successful strategy.

Fostering awareness

As endocrinologists, we need to be aware of this complication and ask about symptoms in all patients after gastric bypass surgery. In my experience, many patients have been struggling to self-manage these symptoms and are relieved to learn that this is a recognized complication and treatment options exist. Many patients respond well to dietary modification and acarbose alone. Those patients with the most severe and difficult to control symptoms are challenging. Surgical options should be considered as a last resort, as their effectiveness is unclear and there is obvious associated morbidity. Ongoing research efforts continue to determine the underlying etiology of this disorder and therapeutic options, including nutritional, pharmacologic and surgical approaches.

In the meantime, treatment of these challenging patients requires a bit of creativity, good communication with the patient and the rest of the care team (nutritionists, bariatric surgeons and gastroenterologists), and attention to the latest advances in the literature. Most importantly, we will need to further determine the frequency of this complication and carefully consider this when we weigh the risks and benefits of Roux-en-Y gastric bypass procedures.

With an increasing number of these procedures being performed every year and with a recent push to consider this procedure as a curative therapy for type 2 diabetes, it is crucial to learn more about this serious complication so we can educate patients about the risks and hopefully identify those at highest risk before the procedure.

Dawn Belt Davis, MD, PhD, is an assistant professor in the section of endocrinology, diabetes and metabolism at the University of Wisconsin-Madison and is a member of the Endocrine Today Editorial Board.