NPPB and pulmonary arterial hypertension: Regarding PAH patients with free 25(OH)vitD levels below vs. those above the median, we found that PAH patients with lower free 25(OH)vitD levels had a more advanced functional class (Figure 6A) and higher levels of BNP/NT-proBNP (p < 0.05, chi-square for trend, Figure 6D).