Background: Hypophosphatemia and bone disease are common in HIV-positive (HIV+) patients on tenofovir disoproxil fumarate-containing antiretroviral therapy (TDF-containing ART). The underlying etiology is not completely understood.
Objective: To examine the effects of treatment of calcium and vitamin D deficiency on phosphate metabolism and bone disease in HIV+ patients on tenofovir.
Methods: This was an open-label, pilot study of calcium and phosphate metabolism, bone turnover, and bone density in 24 HIV+ patients on TDF, who were receiving a 1-year treatment for vitamin D and/or calcium deficiency according to a predefined protocol. Eight patients without calcium or vitamin D deficiency served as controls.
Results: One-year treatment improved vitamin D levels, decreased serum parathyroid hormone (PTH), and improved calcium balance and bone mineral density. It did not affect the serum levels of PTH-related peptide (PTH-rp) or fibroblast growth factor 23 (FGF-23) nor did it raise serum phosphate levels or decrease renal phosphate loss.
Conclusion: Treatment of calcium or vitamin D deficiency in HIV+ patients on ART including TDF has favorable effects on bone density, but it does not improve serum phosphate levels. Renal phosphate wasting in these patients is not caused by excess PTH, PTH-rp, or FGF-23 nor by vitamin D or calcium deficiency.