The Paracalcitol and ENdothelial fuNction in chronic kidneY disease (PENNY) study [99] showed that paricalcitol reduced serum PTH (−75.1 pg/mL, 95% CI −90.4 to −59.8; p < 0.001) and its action is linked to increased FGF23 levels ( + 107 pg/mL, 95% CI 44 to 170; p = 0.001). Here, FGF23 is linked to chronic kidney disease.