FGF23: Is It Ready for Prime Time?

Since the identification of fibroblast growth factor 23 (FGF23)2 more than a decade ago, interest in this hor-mone has grown dramatically among both nephrolo-gists and endocrinologists. FGF23, initially identified in patients with rare forms of hypophosphatemia, is also increased in patients with chronic kidney disease (CKD). A handful of studies have suggested that in-creased circulating concentrations of FGF23 not only play an important role in the development of second-ary hyperparathyroidism but also are associated with ad-verse systemic effects, including increased mortality and deterioration of renal function—associations that have definitively been confirmed in a new prospective study of 3879 adult patients with CKD (1). Isakova et al. reported that circulating FGF23 concentrations were an indepen