NDT Advance Access published online on March 19, 2008
Nephrology Dialysis Transplantation, doi:10.1093/ndt/gfn084
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Vitamin C deficiency and secondary hyperparathyroidism in chronic haemodialysis patients
1 Renal Research Institute, 207 East 94th Street, Suite 303, New York, NY 10128, USA 2 Department of Nephrology, Vivantes-Klinikum im Friedrichshain, Landsberger Allee 49, 10249 Berlin, Germany 3 Department of Internal Medicine, Krankenhaus der Barmherzigen Bruder, Graz, Austria 4 Department of Health and Clinical Sciences, University of Massachusetts, Lowell, 3 Solomont Way, MA 01854, USA
Correspondence and offprint requests to: Anja Richter, Renal Research Institute, 207 East 94th Street, Suite 303, New York, NY 10128, USA. Tel: +1-646-672-4042; Fax: +1-646-672-4174; E-mail: anjarich{at}gmail.com
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Abstract |
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Background. Maintenance haemodialysis patients often suffer from secondary hyperparathyroidism and serum parathyroid hormone levels may be influenced by nutritional variables.
Methods. We examined serum bio-intact parathyroid hormone (BiPTH) and plasma vitamin C in 117 chronic haemodialysis patients. Plasma vitamin C was measured by high-performance liquid chromatography with electrochemical detection, on samples collected before start of the dialysis treatment.
Results. Plasma vitamin C showed a significant positively skewed distribution, ranging from <2 µM to >300 µM. We found 15% (n = 17) of the patients with severe vitamin C deficiency (<10 µM), 66% (n = 77) in the range 10–80 µM, and 19% (n = 23) with plasma vitamin C >80 µM, the upper limit of normal for non-renal disease population. High plasma vitamin C was associated with lower plasma BiPTH (P = 0.005, one-way analysis of variance), and this association persisted after stepwise multiple regression for other factors known to influence PTH. Low vitamin C levels were also associated with increased serum alkaline phosphatase, a further indicator of the impact of vitamin C status on bone metabolism. Patients who reported dietary vitamin C intake of 
100 mg/day had lower BiPTH (P = 0.015), consistent with findings from plasma measurements of vitamin C. This novel observation of the interaction between PTH and vitamin C may result from effects of vitamin C on cAMP-linked signalling pathways in bone and parathyroid gland.
Conclusions. This finding does not yet warrant therapeutic intervention with supplemental vitamin C to remedy secondary hyperparathyroidism. However, further research may indicate a key interaction between vitamin C and the parathyroid hormone linked signalling pathways, and may uncover mechanisms of therapeutic importance.
Keywords: haemodialysis; metabolic bone disease; secondary hyperparathyroidism; vitamin C
Received for publication: 11. 8.07
Accepted in revised form: 29. 1.08