Correction of hypokalemia by magnesium repletion in familial hypokalemic alkalosis with tubulopathy.

The effect of magnesium treatment on serum potassium and potassium balance was examined in three siblings with a recently described syndrome of hypokalemic alkalosis with renal tubulopathy. Oral magnesium supplementation for 11 days in the three siblings increased mean serum potassium from 2.7 +/- 0.1 meq/liter to 3.3 +/- 0.2 meq/liter (p less than 0.05). In addition, urinary and fecal potassium excretion decreased by about 11 meq/day. Magnesium chloride did not affect plasma renin activity while the patients were supine or upright. In contrast, mean supine plasma aldosterone concentration increased from 5.3 +/- 1.5 ng/dl to 13.2 +/- 4.1 ng/dl (p greater than 0.1) and mean upright plasma aldosterone concentration increased from 17.4 +/- 3.8 ng/dl to 66.1 +/- 7.3 ng/dl (p less than 0.01). These findings suggest that hypokalemia and potassium loss in this disorder may be caused by abnormal magnesium metabolism. The increase in plasma aldosterone concentration may have been caused by the positive potassium balance or a direct effect of magnesium on aldosterone secretion from the adrenal gland.