A 20-year-old woman has recurrent muscle cramps. Serum potassium is 2.7 mEq/L with mild metabolic alkalosis. Serum magnesium is 1.1 mg/dL (low) and 24-hour urinary calcium excretion is 40 mg/day (low). Renin and aldosterone levels are elevated. Blood pressure is normal. Which single additional abnormality is expected?

• A Hypercalciuria
• B Persistent urine pH above 5.5 despite acidaemia
• C Urinary concentrating defect responding to indomethacin
• D Nephrocalcinosis on ultrasound ✓

Explanation

Gitelman syndrome mimics chronic thiazide use, with defective NCCT in the distal convoluted tubule causing hypokalaemic alkalosis, hypomagnesaemia, and characteristically HYPOcalciuria. Chronic potassium depletion raises intracellular pH, increasing citrate reabsorption and promoting calcium phosphate precipitation, so nephrocalcinosis and calcium phosphate stones occur despite low urine calcium. Hypercalciuria and indomethacin-responsive polyuria belong to Bartter syndrome, and persistently alkaline urine belongs to distal RTA.

Reference: Williams Textbook of Endocrinology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.