Effect of Vitamin C on Parathyroid Hormone in Hemodialysis Patients With Mild to Moderate Secondary Hyperparathyroidism

Introduction. 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. Materials and Methods. 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. Results. 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. Conclusions. Administration of intravenous vitamin C in hemodialysis patients noticeably decreased level of PTH, but its effect gradually diminished.