DKK1 and rheumatoid arthritis: In particular, 25-OH-vitamin D was negatively associated with HAQ levels (ρ -0.131, p value 0.038), P1nP serum levels were positively associated with CRP levels (ρ 0.320, p value <0.001), PTH serum levels were positively associated with DAS28-CRP score (ρ 0.134, p value 0.034), sclerostin serum levels were positively associated with GC cumulative dose (ρ 0.145, p value 0.029) and Dkk1 serum levels were positively associated with RA disease duration (ρ 0.129, p value 0.045).