Bone aluminum content in predialysis chronic renal failure and its relation with secondary hyperparathyroidism and...

32 patients with slowly evolving predialysis chronic renal failure, who were not exposed to aluminum-containing antacids, were studied. A low aluminum intake was considered a useful condition to examine the bone deposition of the element as dependent variable, not interfering with PTH secretion and bone metabolism. Iliac bone biopsies for bone aluminum content and histomorphometric and histodynamic evaluations were taken. Serum aluminum, creatinine, calcium, phosphate, iPTH, osteocalcin (BGP), alkaline phosphatase (AP), 25-OHD3 and 1,25(OH)2D3 were also measured. 16 of the patients were on long-term treatment with 1,25(OH)2D3 (0.25 micrograms daily) for prevention and treatment of secondary hyperparathyroidism. Bone aluminum content of all patients showed a strong positive correlation with BGP and iPTH (p less than 0.001) while the correlation with serum creatinine was not significant. Multiregression analysis has singled out BGP as the most predictive variable of bone aluminum content (r2 = 0.419). The patients receiving 1,25(OH)2D3 had lower iPTH (p less than 0.01), lower bone aluminum content (p less than 0.05) and increased mineral apposition rate (p less than 0.05) compared to the untreated group. The results suggest that treatment with 1,25(OH)2D3 for long-term suppression of secondary hyperparathyroidism does not enhance aluminum accumulation in bone. The finding of lower bone aluminum together with increased mineral apposition rate, seems to indicate that 1,25(OH)2D3 is able to induce an osteoid mineralization process more selective against aluminum incorporation in bone than in case of more severe hyperparathyroidism and 1,25(OH)2D3 deficiency. At least in the present condition of low aluminum intake, 1,25(OH)2D3 may be considered to have protective effects on bone from aluminum deposition.