24-hour urine metanephrine excretion in patients diagnosed with adrenal incidentaloma: impact of commonly used drugs on a clinical decision.

Introduction: Incidentaloma is an adrenal tumor detected during diagnostic imaging performed for extra‑adrenal causes. Evaluation of metanephrine concentrations in a 24‑hour urine collection can be a significant challenge in patients with multiple medications and comorbidities.
Objectives: The aim of this study was to evaluate the effect of commonly used groups of drugs on metanephrine levels in the 24‑hour urine collection.
Patients and Methods: A total of 1051 patients with adrenal mass below 10 Hounsfield units on unenhanced computed tomography were included in the study. Patients diagnosed with Cushing or Conn syndrome, adrenal carcinoma, pheochromocytoma, active extra‑adrenal malignant neoplasms, and exacerbation of severe illnesses were excluded. Metanephrine, normetanephrine, and 3‑methoxytyramine in the 24‑hour urine collection were measured by high‑performance liquid chromatography with electrochemical detection. Information on concomitant medication (β‑blockers, calcium channel blockers [CCBs], loop diuretics, thiazide diuretics, potassium‑sparing diuretics, α‑blockers, angiotensin‑converting enzyme inhibitors / angiotensin II receptor blockers, metformin, nonmetformin antidiabetic drugs [NMADs], lipid‑lowering drugs, proton pump inhibitors, levothyroxine, thyreostatics, antidepressants, neuroleptics, benzodiazepines, glucocorticosteroids, inhaled B‑receptor agonists, and ipratropium) was collected from each patient.
Results: The urinary excretion of normetanephrine was significantly higher in the patients on β‑blockers, CCBs, loop diuretics, α‑blockers, NMADs, and neuroleptics. α‑Blockers increased urine metanephrine concentration, and NMADs, antidepressants, and glucocorticosteroids lowered it. There was no association between the analyzed drugs and urinary 3‑methoxytyramine level.
Conclusions: Many drug groups interfere with the measurement of urinary fractionated metanephrines. These interactions should be taken into account during interpretation of a hormonal evaluation, as they can be crucial for further management, especially for making a decision on surgical treatment.