Gitelman Syndrome Unmasked in the Setting of Hyperthyroidism: A Diagnostic Challenge in a Low Resource Setting

Abstract

Gitelman Syndrome (GS) is a rare autosomal recessive renal tubulopathy caused by inactivating mutations in the SLC12A3 gene, characterised by hypokalemia, hypomagnesemia, hypocalciuria, and metabolic alkalosis. Hyperthyroidism - most commonly Graves’ disease -independently produces hypokalemia through intracellular potassium shift mediated by upregulated Na+-K+-ATPase activity, a phenomenon termed Thyrotoxic Periodic Paralysis (TPP). When these two conditions coexist, the electrolyte derangements are synergistic, creating a more severe and refractory clinical picture that is prone to misdiagnosis. We report a 28-year-old male from northern India presenting with episodic muscle weakness, palpitations, and profound hypokalemia (serum potassium 2.6 mmol/L) in the context of biochemically confirmed Graves’ disease (TSH<0.01 mIU/L, TRAb positive). Persistent hypokalemia, hypomagnesemia, and hypocalciuria (urine calcium:creatinine ratio 0.04) following restoration of euthyroidism raised suspicion for an underlying tubulopathy. A diagnosis of GS was established on clinical and biochemical criteria without genetic testing - a pragmatic approach in our low-resource setting. The patient responded to carbimazole, propranolol, oral potassium chloride, magnesium oxide, and low-dose spironolactone, with serum potassium improving to 3.2 mmol/L and serum magnesium to 0.68 mmol/L at three-month follow-up, with no further paralytic episodes. This case highlights the importance of recognising GS as a co-existing diagnosis when hypokalemia persists after hyperthyroidism is controlled.

Citation

Rahul Garg. Gitelman Syndrome Unmasked in the Setting of Hyperthyroidism: A Diagnostic Challenge in a Low-Resource Setting. WebLog J Clin Case Rep. wjccr.2026. f2902. https://doi.org/10.5281/zenodo.21323187