Hypomagnesemic hypocalcemia in chronic renal failure.

Hypomagnesemic hypocalcemia in chronic renal disease is a rare finding. Controversy remains regarding the role of decreased magnesium in producing impaired parathyroid hormone (PTH) secretion versus target organ unresponsiveness to PTH. We describe six patients with severe chronic renal disease in whom hypocalcemia and hypomagnesemia were detected. Five patients had chronic interstitial nephropathy; all of them showed renal magnesium wasting. One patient had chronic glomerulonephritis and a malabsorption syndrome and showed a low rate of urinary excretion of magnesium. The administration of magnesium increased calcium levels in all patients. We have found elevated PTH levels in absolute terms, which, however, were inappropriate to correct hypocalcemia; the PTH levels increased in three patients and not in the other three after magnesium replacement. We conclude that in patients with tubulointerstitial nephropathies, chronic renal losses of magnesium can produce hypomagnesemic hypocalcemia.