Jørgensen and colleagues1 measured the levels of, and analyzed the correlations between, different vitamin D metabolites, parathyroid hormones (PTH), and fibroblast growth factor-23 (FGF-23) in anephric patients before and after kidney transplantation. They demonstrated that in these patients, 1α,25(OH)2D levels closely correlated with 25(OH)D rather than with PTH or FGF-23 levels. However, this regulatory relationship was restored post-transplantation. We commend the authors for their elegant findings and would like to extend their results by discussing the relevance of the free hormone theory.