Magnesium deficiency and bone loss after cardiac transplantation.

Magnesium depletion adversely affects many phases of skeletal metabolism and has been implicated as a risk factor in several forms of osteoporosis. Magnesium deficiency has also been reported after cardiac transplantation. To evaluate whether altered magnesium homeostasis could be related to the pathogenesis of early bone loss after cardiac transplantation, we prospectively measured serum and urinary magnesium and evaluated them with respect to biochemical indices of mineral metabolism and rates of bone loss. The study population included 60 patients (45 men, 15 women) aged 53 +/- 11 years (SD) with measurements of biochemistries and bone mineral density by dual-energy X-ray absorptiometry before and 3 months after transplantation. All received prednisone, cyclosporine A, and azathioprine, plus calcium (1000 mg) and vitamin D (400 IU). After transplantation, serum magnesium decreased by 16 +/- 15% (SD) from 2. 0 +/- 0.3 mg/dl to 1.6 +/- 0.2 mg/dl (normal 1.8-2.2 mg/dl; p < 0. 0001), accompanied by an increase in the fractional excretion of magnesium (7.1 +/- 3.9% to 13.3 +/- 5.6%; p < 0.0017). Forty-three patients with low 3-month serum magnesium levels (