Relationship between vitamin D and muscle size and strength in patients on hemodialysis

Objective: Vitamin D has various actions in skeletal muscle. The purpose of this study was to compare lower-limb muscle size and strength in hemodialysis (HD) patients being treated with 1,25-dihydroxyvitamin D (calcitriol) or a 1,25-dihydroxyvitamin D analogue (paricalcitol) with lower-limb muscle size and strength in HD patients who were receiving none. Design: This was a retrospective, cross-sectional study. Setting: This study was performed in outpatient HD centers. Patients: Hemodialysis patients receiving calcitriol or paricalcitol (active vitamin D) for control of secondary hyperparathyroidism (VitD, n = 49) were compared with HD patients who were not (n = 30). Main Outcome Measures: The main outcome measures included the cross-sectional areas (CSAs) of the thigh and tibialis anterior muscles by magnetic resonance imaging, and three measures of strength: the three-repetition maximum (3RM) for knee extension (isotonic), the peak torque of knee extensors (isokinetic), and maximal voluntary contraction of the ankle dorsiflexor muscles (isometric). Results: There were no differences in age, weight, dialysis vintage, or intact parathyroid hormone levels between groups, although serum albumin was higher in the VitD group (P < .05). Patients in the VitD group had a larger thigh-muscle CSA (P < .05) and were stronger across all strength measures (P < .05) after controlling for age and gender (by analysis of covariance). When all analyses were subsequently adjusted for serum albumin concentration, only the difference in 3RM knee-extension strength lost significance. There were no significant differences in any measurements between patients who received calcitriol or paricalcitol. Conclusion: Treatment with active vitamin D was associated with greater muscle size and strength in this cohort of HD patients. (C) 2007 by the National Kidney Foundation, Inc.