OBJECTIVES: Previous studies have suggested a relationship between low serum levels of vitamin D and lupus. Vitamin D receptor ligands can mediate immunosuppressive effects and low levels of this hormone have been proposed as contributing to the immune activation in lupus and other autoimmune diseases. We sought to investigate the prevalence of vitamin D insufficiency in our patients with lupus. METHODS: Serum levels of 25-OH vitamin D were measured in 37 female patients with lupus using an enzyme-linked immunoassay. Correlations with clinical and immunologic measures were determined. RESULTS AND CONCLUSIONS: Approximately 65% of the patients with lupus had values less than 80 nmol, which is accepted as the lower limit of vitamin D adequacy. In addition, 20% of the subjects had levels of 25-hydroxyvitamin D that were lower than the normal range for the assay (<47.7 nmol/L). The group of patients with these lowest levels showed disease activity measures, including global assessment scores, that were higher in the than in those with levels considered normal in the assay (P ≤ 0.003). However, levels of autoantibodies including dsDNA were higher in the group with levels of vitamin D that were greater than 47.7 nmol/L (P = 0.0069). The increased disease symptoms present in patients with very low levels of vitamin D suggests a role for supplementation with exogenous vitamin D to optimize therapeutic outcomes. However, the possibility that such treatment could lead to increased autoantibody levels requires further study.
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