The influence of glomerular filtration rate and age on fibroblast growth factor 23 serum levels in pediatric chronic kidney disease.
BACKGROUND
Fibroblast growth factor 23 (FGF23) is a phosphaturic factor and a suppressor of 1alpha-hydroxylase activity in the kidney. Although its importance in chronic kidney disease (CKD) has been demonstrated in adults, there is little information in pediatric patients.


OBJECTIVE
The aims of this study were: 1) to determine reference values for FGF23 serum levels according to glomerular filtration rate (GFR) (measured by the reference standard, inulin clearance), gender, and age; and 2) to evaluate the effects of different etiologies and treatments on FGF23 serum levels in a prospective single-center cohort of 227 CKD children (119 boys).


RESULTS
Age, body weight, height, and GFR (mean +/- sd) values were: 11.3 +/- 4.1 yr, 37 +/- 16 kg, 140 +/- 20 cm, and 98 +/- 34 ml/min per 1.73 m(2), respectively. Calcium, phosphate, PTH, 25 hydroxyvitamin D, 1,25 dihydroxyvitamin D, C-terminal FGF23, and intact FGF23 (mean +/- sd) levels were: 2.43 +/- 0.11 mmol/liter, 1.41 +/- 0.22 mmol/liter, 41 +/- 23 pg/ml, 24 +/- 10 ng/ml, 152 +/- 72 pmol/liter, 76 +/- 134 relative units/ml, and 44 +/- 37 pg/ml, respectively. There was a wide range of FGF23 serum levels, but FGF23 levels increased when GFR decreased. FGF23 serum levels were not modified by gender, but they increased with age. In univariate analysis, corticosteroid therapy seemed to be associated with increased FGF23 serum levels. A multivariate linear regression analysis found a significant impact of GFR, body mass index, and solid organ transplantation on FGF23 serum levels.


CONCLUSIONS
Age, GFR, body mass index, and solid organ transplantation seem to influence FGF23 serum levels in a pediatric population. The impact of corticosteroids on FGF23 metabolism should be further investigated; further longitudinal studies will also help to better define the prognostic impact of FGF23 serum levels in pediatric CKD in terms of disease progression, cardiovascular morbidities, and bone disabilities.
Bacchetta
Justine
J
Centre de Référence des Maladies Rénales Rares, Hôpital Femme Mère Enfant, Boulevard Pinel, 69677 Bron Cedex, France. justine.bacchetta@chu-lyon.fr
Dubourg
Laurence
L
Harambat
Jérome
J
Ranchin
Bruno
B
Abou-Jaoude
Pauline
P
Arnaud
Simone
S
Carlier
Marie-Christine
MC
Richard
Michel
M
Cochat
Pierre
P
D000293:Adolescent; D000305:Adrenal Cortex Hormones / Q000627:therapeutic use; D000375:Aging / Q000502:physiology*; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D002648:Child; D002675:Child, Preschool; D002940:Circadian Rhythm / Q000502:physiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000097:blood*; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006728:Hormones / Q000097:blood; D006801:Humans; D007444:Inulin; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology* / Q000628:therapy; D016030:Kidney Transplantation / Q000502:physiology; D007684:Kidney Tubules / Q000378:metabolism; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D012727:Sex Characteristics; D014815:Vitamins / Q000097:blood; D014882:Water-Electrolyte Balance / Q000502:physiology; D055815:Young Adult
D000305:Adrenal Cortex Hormones; C000717427:FGF23 protein, human; D006728:Hormones; D014815:Vitamins; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D007444:Inulin