A 60-year-old man presents with symptoms of polyuria and nocturia. Investigations reveal a normal fasting glucose and calcium level. His urine electrolytes suggest a renal transport defect. Which of the following is the most likely cause for his symptoms?

Other clues to renal tubule defects include electrolyte disorders, renal osteodystrophy, large kidneys, and proteinuria. Categories of tubulointerstitial kidney disease include toxins (exogenous and metabolic), neoplasia, immune diseases, vascular disorders, infections, and hereditary renal diseases. Defects in urinary acidification and concentrating ability are frequently the most troublesome manifestations of tubulointerstitial kidney disease.