Serum melatonin levels in ankylosing spondilitis: correlation with disease activity.

This study was carried out to determine the serum levels of melatonin (MLT) in patients with ankylosing spondilitis (AS) and to evaluate its correlation with disease activity. We assessed clinical characteristics and labaratory parameters. Serum samples from 36 patients (25 males, 11 females) with active AS and 25 healthy subjects (18 males, 7 females) were collected. MLT levels were measured by enzyme-linked immunosorbent assay, and disease activity of AS was assessed according to the Bath AS disease activity index (BASDAI), the erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP). Then, the results were compared with those from 25 healty controls. The serum levels of MLT were significantly increased in AS patients as compared to healthy controls (p < 0.05). MLT levels were correlated with BASDAI (r = 0.871, p < 0.001) and CRP levels (r = 0.691, p < 0.001), but not with ESR, in patients with AS. Our results suggest a possible role for this immunoregulatory hormone in the disease activity in AS patients.