To date, therapies with activated vitamin D are only approved for treating secondary hyperparathyroidism in CKD; a large body of experimental and clinical data, however, suggests that vitamin D and its analogues positively affect several factors enhancing the progression of CKD, like anemia, urinary protein excretion, activation of renin-angiotensin system and inflammation [21–25]. Here, REN is linked to secondary hyperparathyroidism.