Fibroblast growth factor-23 and mineral metabolism after unilateral nephrectomy.
BACKGROUND
Fibroblast growth factor -23 (FGF-23) is a key regulator of mineral metabolism. It regulates renal phosphate (Pi) reabsorption and calcitriol synthesis, and has an inhibitory effect on parathyroid hormone (PTH) secretion. FGF-23 increases early in chronic kidney disease (CKD), but the regulation of FGF-23 in mild -to -moderate renal dysfunction is not fully understood.


METHODS
Nine healthy kidney donors underwent unilateral nephrectomy. Estimated glomerular filtration rate (eGFR) calculated from cystatin C and parameters of mineral metabolism: (Pi, ionized calcium, biointact PTH, intact FGF-23, calcitriol, and urinary excretion of calcium and Pi) were analysed before surgery, and one day, one week and three to six months after surgery.


RESULTS
On the first post-operative day, PTH increased due to a decrease in the calcium level. One week after nephrectomy, the FGF-23 level increased from 31.8 ± 12.3 pg/mL to 55.8 ± 15.1 pg/mL, while PTH, Pi and calcium levels were unchanged compared towith baseline. On follow-up, eGFR improved compared with its one-week value, and PTH and FGF-23 were unchanged compared towith baseline. The calcitriol level decreased but was in the normal range at all points in time. The total amount of Pi in urine did not change, while the calcium excretion decreased significantly.


CONCLUSIONS
Pi homeostasis after nephrectomy is maintained by PTH on the first day. When serum calcium is stabilized and food intake resumed, FGF-23 rises, possibly in response to the Pi- load in relation to GFR.
Department of Medical Sciences, Uppsala University Hospital, Ing. 30, 5 tr.; UAS, 75185 Uppsala, Sweden. per-anton.westerberg@medsci.uu.se
Per-Anton
PA
Westerberg
Osten
O
Ljunggren
Tobias E
TE
Larsson
Jonas
J
Wadström
Torbjörn
T
Linde
D000368:Aged; D002117:Calcitriol / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000378:metabolism*; D005500:Follow-Up Studies; D005919:Glomerular Filtration Rate / Q000502:physiology; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007668:Kidney / Q000378:metabolism* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009392:Nephrectomy; D010281:Parathyroid Hormone / Q000378:metabolism; D010710:Phosphates / Q000378:metabolism*
C000717427:FGF23 protein, human; D010281:Parathyroid Hormone; D010710:Phosphates; D005346:Fibroblast Growth Factors; D000089703:Fibroblast Growth Factor-23; D002117:Calcitriol; D002118:Calcium