Insulinoma

What is an Insulinoma?

An insulinoma is a small tumor in the beta cells of the pancreas that secretes excess insulin. It is usually benign, but the excess insulin causes dangerously low blood sugar levels, known as hypoglycemia.

About 90-95% of insulinomas are benign and 5-7% are malignant. They occur at a rate of approximately 1 case per million people.

Typical findings

• Occurs in both males and females with a ratio of approximately 2:3.
• Most cases are diagnosed between 40 and 60 years of age.
• Tumor size is usually less than 2 cm, and there may be single or multiple lesions.

Symptoms of insulinoma

• Blurred or double vision
• Confusion and anxiety
• Dizziness and mood swings
• Weakness, sweating, hunger, and tremors
• Sudden weight gain
• Convulsions, seizures, fast heart rate, difficulty concentrating, loss of consciousness or coma

Laboratory and imaging diagnosis

• Serum insulin levels of 10 µU/mL or more (normal less than 6 µU/mL)
• Glucose levels below 40 mg/dL
• C-peptide levels exceeding 2.5 ng/mL
• Pro-insulin levels of 22 pmol/L or greater
• Negative sulfonylurea screen
• Endoscopic ultrasound detects approximately 80% of insulinomas; CT and MRI detect fewer than 50%.

Treatment

• Medical therapy may include diazoxide, somatostatin analogues, glucagon, and streptozocin.
• Surgical removal of the tumor is the preferred treatment, with a high rate of recovery.
• Cryosurgery may be used to destroy abnormal tissue in specific cases.

Key points

• Insulinomas are tumors of the pancreas that secrete extra insulin.
• They can cause severe hypoglycemia, confusion, sweating, weakness, and coma.
• Almost all insulinomas are not cancerous.
• Surgical removal usually cures the condition.