Inclusion Criteria:  Genetically-proven, symptomatic Gitelman syndrome Written informed consent  Exclusion Criteria:  inability to discontinue potassium-sparing diuretics, mineralocorticoid antagonists and NSAIDs; this means inability to reach a potassium level of 2.5 mmol/L or higher with maximally tolerable potassium supplementation after discontinuation of potassium-sparing diuretics pregnancy