PTH and hydrops fetalis: Because 1,25(OH)2D and PTH(1–84) are physiologically interrelated (23), we examined the ratio of these two hormones and found them to be significantly related to HF severity: NYHA class II ratio = 1.14, NYHA class III ratio = 0.47, and NYHA class IV ratio = 0.38 (p<0.001).