VDR and chronic kidney disease: Nevertheless, our finding that the CKD-induced suppression of osteoblastic and osteocytic TNAP activity and accumulation of pyrophosphate in bone did not occur in Fgf23/VDR mutant mice lacking Fgf23 lends additional support to the notion that the CKD-driven increase in Fgf23 secretion suppresses TNAP transcription in an auto-/paracrine manner.