On the other hand, worsening of HF and renal failure in HF patients leads to secondary hyperparathyroidism and increases of circulating FGF-23, both of which impact the synthesis of 1,25(OH)2D. Measurement of the ratios appears therefore as an efficient tool to assess these interrelated players independently of the kidney function. This evidence concerns the gene FGF23 and secondary hyperparathyroidism.