Relationship between vitamin D, IFN-γ, and E2 levels in systemic lupus erythematosus

In this study, we investigated the relationship between vitamin D, interferon-gamma (IFN-γ), and estradiol (E2) in females of childbearing age with inactive systemic lupus erythematosus (SLE). The study included 22 SLE patients, and 21 age- and gender-matched healthy individuals. Serum concentrations of 25-hydroxyvitamin D3 (25(OH)D3), E2, and IFN-γ were measured by radioimmunoassay using the gamma-counter and ELISA. Patients and control subjects were divided into two groups based on their vitamin D levels (25(OH)D3 ≤ 20 ng/mL; 25(OH)D3 > 20 ng/mL). The median values of IFN-γ and E2 were higher in SLE patients compared to the controls, irrespective of vitamin D level (p = 0.001, p = 0.009, p = 0.003, and p = 0.003, respectively). In SLE patients, there was a negative correlation between IFN-γ and 25(OH)D3 (rs = -0.330; p = 0.03) and a positive correlation between IFN-γ and E2 (rs = 0.404; p = 0.007). This study demonstrates an interesting interplay between vitamin D, INF-γ, and E2 in SLE patients with inactive disease.