Match each patient's clinical presentation and laboratory profile, obtained during an episode of documented fasting hypoglycemia, to the most accurate pathophysiologic description of the underlying etiology.
- A 45-year-old nurse with recurrent hypoglycemia. Labs: Elevated serum insulin, suppressed C-peptide, and undetectable proinsulin.Surreptitious injection of a hypoglycemic agent lacking a connecting peptide
- A 62-year-old female with recurrent fasting hypoglycemia. Labs: Elevated serum insulin, elevated C-peptide, elevated proinsulin, and a negative oral hypoglycemic secretagogue screen.Autonomous proliferation of neuroendocrine cells lacking normal feedback inhibition
- A 70-year-old male with dementia presenting with confusion and a blood glucose of 40 mg/dL. Labs: Elevated serum insulin, elevated C-peptide, and a positive oral hypoglycemic secretagogue screen.Ingestion of a compound that artificially closes ATP-sensitive potassium channels on beta cells
- A 58-year-old male with a large solitary fibrous pleural tumor. Labs: Suppressed serum insulin, suppressed C-peptide, and an elevated IGF-II to IGF-I ratio.Paraneoplastic secretion of a peptide that inappropriately activates peripheral insulin receptors
- A 34-year-old female with profound fatigue, weight loss, and hyperpigmentation. Labs: Suppressed serum insulin, suppressed C-peptide, and failure of serum cortisol to rise >18 µg/dL.Autoimmune destruction of the adrenal cortex leading to counter-regulatory hormone deficiency
Answer
The accurate matching pairs exogenous insulin with a lack of connecting peptide, insulinoma with autonomous neuroendocrine proliferation, sulfonylurea ingestion with K-ATP channel closure, Doege-Potter syndrome with paraneoplastic IGF-II secretion, and adrenal insufficiency with counter-regulatory hormone failure.
The diagnostic workup of hypoglycemia relies on measuring insulin, C-peptide, proinsulin, and hypoglycemic agents during a hypoglycemic episode. Exogenous insulin lacks C-peptide. Endogenous hyperinsulinemia (high C-peptide) is split between secretagogue use (positive drug screen, K-ATP channel closure) and insulinoma (negative screen, autonomous tumor). Hypoglycemia with appropriately suppressed insulin points to non-beta cell tumors (IGF-II secretion) or counter-regulatory failure (adrenal insufficiency).
Step-by-Step Solution
Key Concept
Diagnostic differentiation of fasting hypoglycemia using the insulin, C-peptide, and counter-regulatory hormone axis
Estimated Time:2m 0s