ascorbic-acid and Hyperparathyroidism--Secondary

In end-stage renal disease, there is a high incidence of secondary hyperparathyroidism. It is proposed that increasing vitamin C levels by dietary supplementation results in a decrease of parathyroid hormone (PTH) in vitamin C-deficient hemodialysis patients with secondary hyperparathyroidism. The aim of this study was the evaluation of vitamin C administration for reduction of serum PTH level in hemodialysis patients.. Twenty-one hemodialysis patients with serum PTH levels less than 550 pg/mL (but more than 200 pg/mL) were administered intravenous vitamin C, 200 mg, 3 times per week for 3 months. Blood samples for measurement of PTH were obtained at the beginning of the hemodialysis session every month for three months.. The mean level of serum biointact PTH was 333.3 ± 141.3 pg/mL (reference range, 7 pg/mL to 82 pg/mL) at baseline, and it decreased to 256.5 ± 137.2 pg/mL at 1 month (P = .03). The mean PTH level was also lower than the baseline value at 2 months (260.1 ± 123.2 pg/mL, P = .03), while it increased to 328.9 ± 176.0 pg/mL at 3 months, which was still slightly lower than the baseline level (P = .13). In 15 patients (71.4%), serum levels of PTH were lower than the baseline at months 1 to 2, while in the remaining 6 (28.6%), it was higher than the baseline value. At 3 months, 5 of the 15 patients with lower PTH levels up to the 3rd month experienced an increase in these levels again.. Administration of intravenous vitamin C in hemodialysis patients noticeably decreased level of PTH, but its effect gradually diminished.

Topics: Adult; Ascorbic Acid; Dose-Response Relationship, Drug; Female; Follow-Up Studies; Humans; Hyperparathyroidism, Secondary; Injections, Intravenous; Kidney Failure, Chronic; Male; Parathyroid Hormone; Renal Dialysis; Retrospective Studies; Severity of Illness Index; Time Factors; Treatment Outcome; Vitamins

Secondary oxalosis in chronic hemodialyzed patients is caused by impaired renal excretion and inadequate removal of oxalic acid during hemodialysis. Ascorbic acid is a precursor of oxalic acid. We report a parathyroidectomized patient with chronic renal failure, on hemodialysis, who received over a period of several months a total dose of 91.0 g ascorbic acid i.v. The plasma oxalic acid level in this patient was 14-fold higher than in healthy persons. Increased oxalic acid synthesis from its precursor ascorbic acid may be responsible for hyperoxalemia, high content of oxalic acid in myocardium, aorta and lung, and calcium oxalate deposition in soft tissues. Application of high doses of ascorbic acid should be avoided in hemodialysed patients with chronic renal failure.

Topics: Adult; Aorta; Ascorbic Acid; Calcinosis; Calcium Oxalate; Cardiomyopathies; Humans; Hyperparathyroidism, Secondary; Lung; Male; Nephritis, Interstitial; Parathyroid Glands; Renal Dialysis; Uremia