• Incidence 2:1000 000 per year
• 90% Benign
• 10% multiple
• 10% MEN1
• Median age 6th decade
• Tumours are usually small 0.5 to 5cm and occur in any part of the pancreas

Insulinoma Syndrome

• Neuroglycopenic Symptoms

1. funny turns especially after fasting
2. Altered mood, behaviour and personality
3. Neurological disturbance

• Autonomic Symptoms

1. palpitations, tremor and sweating

Insulinoma Diagnosis

• Prolonged Supervised Fast: Used to demonstrate fasting hypoglycaemia and diagnose insulinoma

• Preparation: Admit to perform test under close supervision with glucose (p.o./i.v.) available.

• Method:

1. Cannulate patient and commence 72 hr fast.
2. Water/non-caloric beverages allowed. Patient should be active during waking hours.
3. Blood glucoses should be done at regular (4-6 hr) intervals and whenever the patient has symptoms suggestive of hypoglycaemia.

If blood glucoses are = 2.2 mmol/l or symptoms are convincing:

• Take blood for glucose, insulin and C-peptide
• Take blood and spot urine for sulphonylurea screen
• Ring biochemistry up for an urgent glucose.
• Do not reverse hypoglycaemia until the lab confirms hypoglycaemia, or unless

The patient becomes unconscious or fits. If no symptoms during the fast, finish with 15-30 mins exercise, e.g. a brisk walk around the hospital.

• Take final samples for glucose, insulin and C-peptide, sulphonylurea screen.

• Interpretation:

1. Normals do not become hypoglycaemic, although young women can run glucoses in the region of 2.2-3.0 without symptoms.
2. True hypoglycaemia must be demonstrated (glucose = 2.2 mmol/l), before we are able to either interpret insulin results or consider insulinoma. With hypoglycaemia endogenous insulin production (estimated by C-peptide) should be low.
3. Hypoglycaemia with raised insulin but low C peptide - consider self administration of insulin.
4. Hypoglycaemia with raised insulin and raised C-peptide - make sure sulphonylurea screen is negative.

• Localisation

1. USS +/- endoscopic
2. CT & MRI
3. Octreotide scan
4. Visceral angiography +/- stimulation

Visceral angiography +/- stimulation

Performed in patients with proven gastrinomas or insulinomas, whose tumours are too small (usually less than 1 cm) to be detected by CT or USS.
Highly selective angiography performed.
Intra-arterial calcium used to stimulate insulinoma.

Treatment

Medical:

• Multiple, regular, small meals.
• Guar gum - slows gastric absorption.
• Steroids - helpful for a short period.
• Diazoxide - s/e hypokalaemia and severe oedema.
• Octreotide - s/e hypoglycaemia if glucagon levels are suppressed.

Surgery

Hepatic embolisation

• the liver has a dual blood supply (hepatic artery and portal vein)
• embolization of hepatic arterial supply (which supplies tumour) using foreign substances (e.g. polyvinyl alcohol). Patent portal circulation (necessary to sustain liver function).