DENVER—Elevated levels of fibroblast growth factor 23 (FGF-23) are independently associated with an increased risk of mortality and death-censored graft loss in renal transplant recipients, data show.

FGF-23 is a hormone secreted by osteocytes and osteoblasts that regulates phosphorus and vitamin D metabolism.

Istvan Mucsi, MD of McGill University in Montreal and Semmelweis University in Budapest, Hungary, and colleagues studied 984 stable renal transplant recipients. The mean age of the sample was 51 years and the median transplant vintage was 72 months. The study population was 57% male and the mean estimated glomerular filtration rate was 51 mL/min/1.73 m2.

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During 37 months of follow-up, 87 patients died and 101 returned to dialysis. Each 1 log-unit increase in FGF-23 was associated with a 78% increased risk of death and 60% increased risk of death-censored graft loss, after adjusting for multiple variables. Compared with patients in the lowest tertile of FGF-23, those in the highest tertile had a 2.3 times increased risk of death and a nearly threefold increased risk of death-censored graft loss. The results were robust to multiple analytical strategies and sensitivity analyses.

“The consistent finding of increased risk of mortality, cardiovascular disease, and CKD progression among patients with increased FGF23 levels across the diverse clinical settings of dialysis, pre-dialysis, non-CKD, and now, kidney transplantation, supports the possibility of FGF-23 toxicity,” Dr. Mucsi said. “The fact that the association between increased serum FGF-23 levels and mortality was present even in kidney transplant recipients, many of whom had low-normal or normal serum phosphorus level, gives further support to this hypothesis.”