Direct effect of the correction of acidosis on plasma parathyroid hormone concentrations, calcium and phosphate in hemodialysis patients: a prospective study.
BACKGROUND
Metabolic acidosis contributes to renal osteodystrophy and together with hyperphosphatemia, hypocalcemia and altered vitamin D metabolism may result in increased levels of intact parathyroid hormone (iPTH) and metastatic calcifications. However, the impact of the correction of metabolic acidosis on iPTH levels and calcium-phosphate metabolism is still controversial.


METHODS
The effects of the correction of metabolic acidosis on serum concentrations of iPTH, calcium (Ca), phosphate (PO(4)) and alkaline phosphatase were prospectively studied. Twelve uremic patients on maintenance hemodialysis (HD) for 49 months (median; range 6-243 months) with serum bicarbonate levels < or =20 mmol/l were studied before and after 3 months of oral sodium bicarbonate supplementation. Predialysis serum bicarbonate, arterial pH, ionized calcium, plasma sodium, plasma potassium, serum creatinine, hemoglobin, K(t)/V, postdialysis body weight, predialysis systolic and diastolic blood pressure were also evaluated before and after correction.


RESULTS
Serum bicarbonate levels and arterial pH increased respectively from 19.3 +/- 0.6 to 24.4 +/- 1.2 mmol/l (p < 0.0001) and 7.34 +/- 0.03 to 7.40 +/- 0.02 (p < 0.001). iPTH levels decreased significantly from 399 +/- 475 to 305 +/- 353 pg/ml (p = 0.026). No changes in total serum Ca, plasma PO(4), serum akaline phosphatase, K(t)/V, serum creatinine, hemoglobin, body weight, predialysis systolic and diastolic blood pressures were observed. iCa decreased significantly.


CONCLUSIONS
Our study demonstrates that the correction of metabolic acidosis in chronic HD patients reduces iPTH concentrations in HD patients with secondary hyperparathyroidism possibly by a direct effect on iPTH secretion.
Movilli
E
E
Division of Nephrology Spedali Civili and Chair of Nephrology, University of Brescia, P. le Ospedale Civile,1, I-25123 Brescia, Italy.
Zani
R
R
Carli
O
O
Sangalli
L
L
Pola
A
A
Camerini
C
C
Scolari
F
F
Cancarini
G C
GC
Maiorca
R
R
D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000097:blood* / Q000209:etiology / Q000628:therapy*; D000328:Adult; D000368:Aged; D000469:Alkaline Phosphatase / Q000097:blood; D002117:Calcitriol / Q000627:therapeutic use; D002118:Calcium / Q000097:blood*; D005260:Female; D006801:Humans; D006962:Hyperparathyroidism, Secondary / Q000150:complications / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood*; D010710:Phosphates / Q000097:blood; D011446:Prospective Studies; D012044:Regression Analysis; D006435:Renal Dialysis; D017693:Sodium Bicarbonate / Q000008:administration & dosage; D014511:Uremia / Q000097:blood* / Q000150:complications / Q000628:therapy
D010281:Parathyroid Hormone; D010710:Phosphates; D017693:Sodium Bicarbonate; D000469:Alkaline Phosphatase; D002117:Calcitriol; D002118:Calcium