A 43-year-old woman comes to the office due to episodic confusion, blurred vision, tremors, and sweating. The episodes have increased in intensity in the past few months and seem to occur any time during the day. Her symptoms are relieved by drinking orange juice. During a recent episode, the patient's blood glucose level was 32 mg/dL as measured by her husband's home glucose meter. Medical history includes major depression and irritable bowel syndrome. Laboratory studies performed during the next episode of symptoms show the following results: Which of the following is the most likely cause of this patient's symptoms?

Question

A 43-year-old woman comes to the office due to episodic confusion, blurred vision, tremors, and sweating.  The episodes have increased in intensity in the past few months and seem to occur any time during the day.  Her symptoms are relieved by drinking orange juice.  During a recent episode, the patient's blood glucose level was 32 mg/dL as measured by her husband's home glucose meter.  Medical history includes major depression and irritable bowel syndrome.  Laboratory studies performed during the next episode of symptoms show the following results:  Which of the following is the most likely cause of this patient's symptoms?

Quizplus · Accepted Answer

11ec160b_3914_8500_9249_91625e25deaa_MD0001_00 This patient has symptomatic hypoglycemia, confirmed by the Whipple triad: Insulin is initially synthesized as preproinsulin, after which the signal peptide is removed, yielding proinsulin. In the secretory granules, proinsulin is cleaved into insulin and C-peptide, which are then released together in equimolar amounts. Normally, as blood glucose falls, endogenous insulin secretion is suppressed, and serum levels of both insulin and C-peptide drop. Hypoglycemia due to excessive endogenous insulin production is associated with elevated levels of C-peptide. This can occur due to autonomous insulin-producing tumors (insulinomas) or intake of insulin secretagogues (eg, sulfonylureas). Self-induced hypoglycemia via oral hypoglycemics is often a manifestation of a factitious disorder and is typically seen in health care workers and family members of patients with diabetes using these medications (which is likely in this patient whose husband has home glucose-testing supplies). Sulfonylurea abuse can be confirmed by testing the urine or blood for specific hypoglycemic agents. (Choice A) Glucagonoma is a rare tumor of pancreatic alpha cells that secretes excessive amounts of glucagon. This results in hyperglycemia, weight loss, anemia, and necrolytic migratory erythema (a raised, erythematous rash affecting the face, groin, and extremities). (Choice B) Hypoglycemia due to exogenous insulin injection, which does not contain C-peptide, is associated with an elevated serum insulin level but an undetectable C-peptide level. (Choice C) Somatostatinoma is a rare tumor of pancreatic delta cells that is associated with hyperglycemia, weight loss, abdominal pain, steatorrhea, cholelithiasis, and hypochlorhydria. These manifestations are due to somatostatin-induced inhibition of insulin, gastrin, secretin, and cholecystokinin secretion, as well as decreased gastrointestinal motility. (Choice E) VIPomas are non-beta cell pancreatic islet cell tumors that hypersecrete vasoactive intestinal polypeptide (VIP). Features include watery diarrhea, hypokalemia, and impaired gastric acid secretion. Educational objective: Hypoglycemia is characterized by tremor, diaphoresis, and confusion in association with a low blood glucose level and resolution of symptoms when the blood glucose level is corrected. Hypoglycemia with elevated insulin and low C-peptide levels suggests exogenous insulin injection, whereas elevated C-peptide suggests an insulin secretagogue or insulin-secreting tumor. __________ References: Approach to the patient with spontaneous hypoglycemia. (http://www.ncbi.nlm.nih.gov/pubmed/24641805)

A 43-Year-Old Woman Comes to the Office Due to Episodic