What screening test can be used to differentiate between insulinoma and sulfonylurea abuse?

The secretagogue screen is instrumental in distinguishing between insulinoma and sulfonylurea abuse because it measures the levels of insulin and C-peptide in the blood after administration of a glucose load. In cases of insulinoma, the tumor produces endogenous insulin, typically resulting in elevated levels of both insulin and C-peptide. In contrast, sulfonylurea therapy leads to increased insulin secretion, but it may not result in elevated C-peptide levels, as the exogenous administration of the drug can alter the natural secretion dynamics.

By analyzing both insulin and C-peptide levels, healthcare providers can determine whether the source of excess insulin is endogenous (from insulinoma) or exogenous (from sulfonylurea medications). Thus, this test provides critical differentiation between the two conditions, aiding in accurate diagnosis and subsequent management.

The other options, while relevant in the context of insulin regulation, do not provide the same level of clarity when it comes to distinguishing between insulinoma and sulfonylurea use. For example, the insulin tolerance test assesses insulin sensitivity but does not differentiate the cause of hyperinsulinemia. The glucose tolerance test evaluates how the body processes glucose over time but does not specifically target insulinoma versus sulfonylurea