Most common of all functioning pancreatic endocrine tumors (PET)


Most common of all functioning pancreatic endocrine tumors (PET)

Highest incidence in 4th to 6th decade

Women are slightly more affected

All insulinomas are located in the pancreas and tumors are equally distributed

90% are solitary and 90% are small ( < 2cm)

10% are multiple (always associated with MEN 1) and 10% are malignant

Clinical features: Abdominal discomfort, sweating, hunger, dizziness, diplopia, overeating, and obesity

Whipple’s triad

Symptoms of hypoglycemia after fasting or exercise

Symptoms of hypoglycemia (blood sugar < 45mg %)

Immediate relief after I.V. glucose administration


A fasting test that lasts for upto 72 hours is the most sensitive test

Insulin, Proinsulin, C-peptide and blood glucose are measured at 1 to 2 hour intervals to demonstrate high secretion of insulin in relation to blood glucose

Continuous C-peptide levels demonstrate the endogenous insulin secretion and exclude factitious hypoglycemia caused by insulin injection

Insulin radioimmunoassay

Insulin level > 7 µU/ml

Insulin/glucose ration > 0.3

Increased circulating C-peptide

Proinsulin level >24% of total insulin signifies insulinoma

Proinsulin level >40% of total insulin signifies malignant insulinoma

For preoperative localization: Endoscopic ultrasound(EUS) has the highest sensitivity


Enucleationis the treatment of choice for benign insulinomas

For superficial tumors: laparoscopic enucleation

Tumors located deep in the body or tail and those in close proximity to pancreatic duct: distal pancreatectomy

Diazoxide suppresses insulin secretion and offers good control of hypoglycemia

Malignant insulinomas: aggressive resection

When surgery cannot be applied for malignant insulinomas: Chemotherapy (Doxorubicin + Streptozocin)