Case Presentation:
A 34-year-old female with history of Systemic Lupus Erythematosus and gastroparesis status post Roux-en-Y gastric bypass (RYGB) surgery, was admitted for intractable nausea and vomiting. CT scan of abdomen and pelvis showed large stool burden. Conservative treatment was implemented. During her hospital course, she developed symptomatic hypoglycemia (blood glucose <40mg/dL), that recurred despite continuous infusion of Dextrose 10%. Hypoglycemia occurred both during fasting and post-prandial states. Her investigations revealed low venous plasma glucose levels, elevated proinsulin, and inappropriately normal insulin and C-peptide levels. A urine sulfonylurea/meglitinide test returned negative. An abdominal CT scan with pancreatic protocol did not reveal any lesions. An endoscopic ultrasonography of the pancreas showed no abnormalities, but was a technically suboptimal study due to patient’s post-surgical anatomy. Due to lack of evidence to suggest an insulinoma, non-insulinoma pancreatogenous hypoglycemia syndrome (NIPHS) was suspected. A core needle biopsy of the pancreas showed benign pancreatic acinar tissue. As patient declined any surgical option, she was started on total parenteral nutrition (TPN) and diazoxide. Hypoglycemic symptoms resolved and blood glucose remained > 60 mg/dL afterwards.
Discussion:
Hypoglycemia is an uncommon clinical problem in patients not being treated for diabetes mellitus. After the Whipple’s triad is demonstrated, as in this patient with symptoms consistent with hypoglycemia, a low plasma glucose concentration, and relief of the symptoms when the plasma glucose level is raised, the goal of testing is to assess the role of insulin in the genesis of the hypoglycemia. In our patient, her insulin and C-peptide levels suggested the presence of insulinoma or endogenous hyperinsulinemic hypoglycemia, such as NIPHS and nesidioblastosis following RYGB. Imaging tests are useful to distinguish between the presence of an insulinoma versus a diffuse process. Findings on pathology confirm the presence of nesidioblastosis. For patients with severe hypoglycemia, graded pancreatectomy is required to control symptoms. However, as this patient was not a surgical candidate, further localizing tests including a selective arterial calcium stimulation test were not performed, and she was instead conservatively treated with diazoxide, a medication that inhibits insulin release.
Conclusions:
Hypoglycemia in non-diabetic patient requires a thorough work-up to determine the etiology. A hyperinsulinemic state in the setting of hypoglycemia (excluding exogenous causes) can be due to insulinoma, NIPHS or nesidioblastosis following RYGB. Differentiating between these conditions can be challenging. In severe cases, surgery is the preferred treatment. However, in patients that are not surgical candidates, a conservative approach can be pursued.