Symptoms during an attack:
(1) hypoglycemia-related: headache, visual disturbances, lightheadedness, confusion, drowsiness, seizures
(2) catecholamine response related: tremors, palpitations, sweating
Clinical features of an insulinoma:
(1) Symptoms occurs when the person fasts.
(2) Symptoms are associated with hypoglycemia with serum glucose < 50 mg/dL.
(3) Symptoms are relieved by the ingestion of carbohydrates.
(4) Serum levels of insulin are elevated.
The first 3 features are referred to as Whipple's triad.
It is important to exclude artifactual hypoglycemia:
(1) The fast is monitored.
(2) Serum samples collected during an attack are free of sulfonylureas or other hypoglcyemic agents.
(3) Serum levels of proinsulin and C-peptide are elevated. In self-injection of insulin these should be low or normal.
Differential diagnosis:
(1) artifactual hypoglycemia
(2) obesity with insulin resistance
(3) autoantibodies against the insulin receptor
