Objectives: Vitamin D (VD) has multiple physiological function including bone-mineral metabolism and musculo-skeletal effects. The purpose of this study is to disclose actual circumstances of VD contentment and characteristics in patients with Rheumatoid Arthritis (RA). 

Methods: Serum VD levels of 132 outpatients with RA consecutively selected in our hospital were estimated. The relationship between serum VD levels and various clinical indices was investigated.

Results: Mean serum concentration of 25-hydroxyvitamin D3 (25OHD) in total subjects was 18.1ng/ml, which was regarded as apparent VD deficiency. Importantly, 60% of the subjects showed less than 20ng/ml, and only 5% exceeded 30ng/ml which fulfilled sufficient VD level. In contrast, mean serum 1α, 25-dihydroxyvitamin D3 level was 37.9 pg/ml, which was within the normal reference value. Disease activity and various serum chemistry data were not related to the VD levels. Instead, there was a tendency that higher Steinbrocker’s functional class was associated with lower serum 25OHD level. 

Conclusion: From these results, we concluded that frequency of VD deficiency in RA patients is high and it is supposed that low physical activity is closely related to VD deficiency. Appropriate VD supplementation should be considered a part of comprehensive management of RA patients.

Keywords: Rheumatoid arthritis; Vitamin D deficiency; 25-hydroxyvitamin D.