Elevated prolactin levels in patients with rheumatoid arthritis: association with disease activity and structural damage.

OBJECTIVES Prolactin (PRL) is a hormone with cytokine-like activities that has been demonstrated to be involved in immune responses. However, there are inconsistent results related to the role of PRL in rheumatoid arthritis (RA). Therefore, the aim of this study was to evaluate the levels of PRL in serum and synovial fluid in patients with RA and osteoarthritis (OA) and examine whether PRL might be associated with laboratory and clinical disease activity of RA. METHODS A total of 29 patients with RA and 26 patients with OA were included in the study. The concentration of PRL in the serum and synovial fluid was measured by immunoradiometric assays, and the levels of serum anti-citrullinated protein/peptide autoantibodies (ACPA) and IgM rheumatoid factor (IgM-RF) were analysed by ELISA. Disease activity score (DAS 28) and radiological (Larsen) score were assessed. RESULTS The levels of PRL in serum (299.55±27.28 vs. 230.59±16.61 mIU/l, p=0.041) as well as in synovial fluid (338.85±33.49 vs. 245.97±21.88 mIU/l, p=0.024) were significantly higher in patients with RA than in patients with OA. A moderate correlation was found between disease activity of RA and levels of PRL in synovial fluid (r=0.485, p=0.010) and the serum PRL levels correlated significantly with the total Larsen score (r=0.484, p=0.014). CONCLUSIONS The findings of increased prolactin levels in patients with RA lead to the assumption that prolactin may play a role in disease severity and the process of joint damage in RA.