Fibroblast growth factor 23 (FGF-23) does not consistently predict declining kidney function or development of CKD in healthy older adults, reports a study in Kidney International.
The analysis included 2496 well-functioning older adults, aged 70 to 79 years at baseline, enrolled in the prospective Healthy Aging and Body Composition study. Fifty-two percent of participants were women and 38% were black. Levels of FGF-23, measured using a commercial assay, were analyzed as a predictor of subsequent decline in kidney function and incident CKD (based on repeated measurements of cystatin C).
The median FGF-23 value was 46 pg/mL; participants with higher FGF-23 levels were more likely to have comorbid conditions including diabetes, hypertension, coronary artery disease, and heart failure. About 28% of older adults had an eGFR decline of greater than 3 mL/min/year, 16% had a 30% decline in kidney function, and 21% had incident CKD.
With adjustment for baseline kidney function and a wide range of other variables, doubling of FGF-23 was not related to any of the three measures of kidney function decline. Participants in the highest quartile of FGF-23 were more likely to develop CKD, compared to those in the lowest quartile: incident rate ratio 1.27. There were no significant interactions between FGF-23 and incident CKD.
Previous studies have reported that FGF-23 is a risk factor for the development of ESRD. Less is known about this hormone’s association with earlier signs of progressive kidney disease.
The new study suggests that FGF-23 is not a strong independent risk factor for declining kidney function or incident CKD in community-dwelling older adults. Initial associations are weakened by adjustment for comorbid conditions, kidney disease risk factors, and indicators of mineral metabolism. The results “suggest that FGF-23 may be a marker of kidney health or function, rather than a mediator of kidney damage, the researchers write [Drew DA, et al. Fibroblast growth factor 23: a biomarker of kidney function decline. Am J Nephrol 2018; 47:242–250].