Association between vitamin D, oestradiol and interferon-gamma in female patients with inactive systemic lupus erythematosus: A cross-sectional study

Objectives To investigate possible associations between 25-hydroxyvitamin D-3 (25(OH)D-3), oestradiol (E-2) and IFN-gamma (IFN) in female patients with inactive systemic lupus erythematosus (SLE). Methods Female patients with inactive SLE and age-matched healthy controls were recruited into this cross-sectional study. Serum concentrations of 25(OH)D-3,D- E-2 and IFN were measured by radioimmunoassay with gamma-counters and enzyme-linked immunosorbent assay. Results 36 patients and 37 controls were enrolled. In patients with SLE, the concentration of 25(OH)D-3 was lower and E-2 was higher compared with controls. In vitamin D deficient (i.e., 25(OH)D(3)20ng/ml) patients, IFN was 150% higher compared with patients with 25(OH)D-3>20ng/ml and controls. The concentration of E-2 was higher in all patients compared with controls independently of the vitamin D level. A difference was found between patients and controls in the correlation of 25(OH)D-3 with E-2 and a positive correlation was found between E-2 and IFN in all participants. Conclusions Our results suggest that E-2 may have a strong modulating effect on vitamin D function which is significant only at low concentration of E-2.