TNFSF11 and rheumatoid arthritis: Patients in the co-morbid group had higher RF, IL-27 and RANKL than those in the RA group, and the differences were statistically significant (P < 0.05); patients in the co-morbid group had lower PINP and 25(OH)D than those in the RA group, and the differences were statistically significant (P < 0.05); while patients in the co-morbid group had slightly higher CRP than those in the RA group, and the differences were not statistically significant..