Association of Vitamin D Metabolites with Parathyroid Hormone, Fibroblast Growth Factor-23, Calcium, and Phosphorus in Dogs with Various Stages of Chronic Kidney Disease.
BACKGROUND
Hypovitaminosis D is associated with progression of renal disease, development of renal secondary hyperparathyroidism (RHPT), chronic kidney disease-mineral bone disorder (CKD-MBD), and increased mortality in people with CKD. Despite what is known regarding vitamin D dysregulation in humans with CKD, little is known about vitamin D metabolism in dogs with CKD.


OBJECTIVES
The purpose of our study was to further elucidate vitamin D status in dogs with different stages of CKD and to relate it to factors that affect the development of CKD-MBD, including parathyroid hormone (PTH), fibroblast growth factor-23 (FGF-23), calcium, and phosphorus concentrations.


METHODS
Thirty-seven dogs with naturally occurring CKD were compared to 10 healthy dogs. Serum 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)2 D], and 24,25-dihydroxyvitamin D [24,25(OH)2 D], and PTH and FGF-23 concentrations were measured. Their association with serum calcium and phosphorus concentrations and IRIS stage was determined.


RESULTS
Compared to healthy dogs, all vitamin D metabolite concentrations were significantly lower in dogs with International Renal Interest Society (IRIS) stages 3 and 4 CKD (r [creatinine]: -0.49 to -0.60; P < .05) but not different in dogs with stages 1 and 2 CKD. All vitamin D metabolites were negatively correlated with PTH, FGF-23, and phosphorus concentrations (r: -0.39 to -0.64; P < .01).


CONCLUSIONS AND CLINICAL IMPORTANCE
CKD in dogs is associated with decreases in all vitamin D metabolites evaluated suggesting that multiple mechanisms, in addition to decreased renal mass, affect their metabolism. This information could have prognostic and therapeutic implications.
['Parker|V J|VJ|', 'Harjes|L M|LM|', 'Dembek|K|K|', 'Young|G S|GS|', 'Chew|D J|DJ|', 'Toribio|R E|RE|']
D000818:Animals D002118:Calcium D016022:Case-Control Studies D003404:Creatinine D004283:Dog Diseases D004285:Dogs D005260:Female D000089703:Fibroblast Growth Factor-23 D005346:Fibroblast Growth Factors D008297:Male D010281:Parathyroid Hormone D010758:Phosphorus D051436:Renal Insufficiency, Chronic D014807:Vitamin D
renal secondary hyperparathyroidism international renal interest society calcitriol diet