Insulinoma (Whipple's Triad) with Case

00:00 Let's go on to another case. A 25-year-old female presents to the emergency department with palpitations, sweating, and blurry vision after playing volleyball on the beach. She denies chest pain and shortness of breath. She states that these symptoms occur often, but resolved after eating a meal or drinking a sugary soda. Past medical history is unremarkable and she takes no medications.

00:26 Temperature is 37°C, blood pressure 135/80, pulse rate 102 beats/minute, and respirations 18. Fingerstick blood glucose level is 42 mg/dL. ECG revealed sinus tachycardia. Urine analysis and toxicology are non-contributory. Appropriate medical therapy is administered and she is discharged with an appointment for a fasting blood draw within the week. These labs show a blood glucose of 14 mg/dL, a C-peptide of 0.8 nmol/L, a serum insulin of 20 microU/L, a serum pro-insulin of 10 microU/L, a negative sulfonylurea, and a negative IGF2. The symptoms of palpitation, sweating, blurred vision all resolved with food and implied the presence of underlying hypoglycemia. This is confirmed on a fingerstick blood glucose and then repeated by a serum blood glucose in both cases revealing low blood glucose or hypoglycemia. The patient's C-peptide level is 0.8 nmol/L. This implies that there is some degree of endogenous insulin production and this is again confirmed by an elevated level of serum insulin and pro-insulin. The sulfonylurea is negative which suggests that she is not taking an oral hypoglycemic. The most likely diagnosis here in this young girl is an insulinoma. Normally, pro-insulin is cleaved into insulin and C-peptide and both are secreted from the pancreas into the bloodstream. Endogenous insulin is manufactured in its active state. It is not cleaved and will not change the C-peptide levels. To rule out insulin overdose or factitious disorder, pro-insulin and C-peptide levels are measured. The patient's C-peptide levels are elevated indicating that she did not inject insulin surreptitiously. Further work-up must be completed for this patient including imaging, ultrasound, CT scan, or MRI of the abdomen to assess for a pancreatic insulinoma. Evaluation for pathologic hypoglycemia.

02:47 When Whipple's triad is present namely symptomatic hypoglycemia, hypoglycemia at less than 55 mg/dL, and the prompt symptomatic relief with the correction of the hypoglycemia. No confirmation of hypoglycemia with glucose monitors but instead use the more accurate serum laboratory method to confirm the fingerstick. The etiology of hypoglycemia in patients without diabetes is mostly caused by drugs. Illness, however, hormone deficiencies, non-islet cell tumors, endogenous hyperinsulinism or non-insulinomas, and pancreatogenous hypoglycemia may be rarer causes. Depletion of hepatic glycogen stores may also contribute. Alcohol ingestion and finally intentional or unintentional use of hypoglycemic agents is also a common cause.