Association of increased active PTH(1-84) fraction with decreased GFR and serum Ca in predialysis CRF patients: modulation by serum 25-OH-D.
As the serum calcium and glomerular filtration rate decreased, the proportion of active PTH(1-84) molecules in PTH immunoreactivity increased in serum from predialysis uremic patients, particularly those with vitamin D insufficiency.


BACKGROUND
The PTH(1-84) fraction was altered in predialysis patients with chronic renal failure (CRF).


METHODS
Serum PTH in predialysis CRF patients without any medication was measured by PTH(1-84)-specific whole PTH assay and intact PTH assay cross-reacting with N-truncated PTH.


RESULTS
In CRF patients, the glomerular filtration rate (GFR) correlated positively with serum Ca and 1,25-dihydroxyvitamin D (1,25(OH)(2)D), and inversely with serum Pi, log intact PTH, and log whole PTH. In multiple regression analysis, including age, gender, body mass index, GFR, Ca, and Pi and 1,25(OH)(2)D as independent variables, serum Ca and GFR associated significantly with serum log whole PTH and intact PTH. Serum log whole PTH/intact PTH ratio, which increased as serum Ca and GFR decreased, retained a negative correlation in those with serum 25-hydroxyvitamin D levels below 20 ng/ml, but not in those above 20 ng/ml. The ratio also correlated positively with serum log tartrate-resistant acid-phosphatase-5b, log cross-linked N-telopeptide of type-I collagen, and log bone alkaline-phosphatase.


CONCLUSIONS
As GFR declined with suppression of serum Ca, the proportion of active PTH molecules increased in predialysis CRF patients, particularly those with vitamin D insufficiency.
Kurajoh
M
M
Department of Metabolism, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka, 545-8585, Japan.
Inaba
M
M
Yamada
S
S
Imanishi
Y
Y
Tsuchida
T
T
Ishimura
E
E
Nishizawa
Y
Y
D000368:Aged; D015415:Biomarkers / Q000378:metabolism; D015519:Bone Density / Q000502:physiology; D001851:Bone Diseases, Metabolic; D016723:Bone Remodeling / Q000502:physiology; D002118:Calcium / Q000378:metabolism*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000378:metabolism*; D012044:Regression Analysis; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000150:complications* / Q000503:physiopathology
D015415:Biomarkers; D010281:Parathyroid Hormone; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium