For a patient with episodic sweating and hunger, what is the most appropriate next investigation after normal fasting plasma glucose?

In the context of a patient experiencing episodic sweating and hunger, symptoms that may suggest hypoglycemia, the most appropriate next step after a normal fasting plasma glucose is to assess the plasma glucose concentration following a prolonged fast. This investigation aims to replicate the conditions under which episodes of hypoglycemia may occur, providing insight into the patient's glucose metabolism and the body's regulatory mechanisms.

A prolonged fast allows observation of how the insulin and glucagon systems respond over time without the influence of recent food intake. This can help in diagnosing potential insulinomas or other causes of inappropriate insulin secretion that may lead to transient hypoglycemic episodes. It's crucial to simulate the conditions under which the patient experiences symptoms to determine whether their body can maintain adequate glucose levels under stress.

Other options would not appropriately address the specific symptoms or the underlying investigation needed. For instance, conducting a CT scan of the pancreas might identify structural lesions but would not provide immediate functional insight into the patient's glucose regulation. Home blood glucose monitoring could offer snapshots of glucose levels but may not capture the dynamic response over an extended period, thereby lacking context for the episodes of sweating and hunger. Measuring serum C-peptide concentration would give information about endogenous insulin production but does not directly test the body's glucose management in the context of prolonged