FGF23 and secondary hyperparathyroidism: Directly targeting FGF23 in CKD is unfavorable as blocking iFGF23 with neutralizing antibodies in a 5/6-nephrectomized CKD rat model reduced survival due to a severe increase in Pi levels and concomitant vascular calcification, although secondary hyperparathyroidism was decreased, calcitriol levels increased, and multiple bone parameters improved [14].