Circulating prolactin level in systemic lupus erythematosus and its correlation with disease activity: a meta-analysis

Objective This study aimed to evaluate the relationship between circulating prolactin level and systemic lupus erythematosus (SLE), and to establish a correlation between plasma/serum prolactin levels and SLE activity. Methods We performed a meta-analysis comparing the plasma/serum prolactin levels in patients with SLE to controls, and examined correlation coefficients between circulating prolactin level and SLE disease activity. Results Twenty-five studies with a total of 1056 SLE patients and 426 controls were included. Prolactin levels were significantly higher overall in the SLE group than in the control group (standardized mean difference (SMD)=0.987, 95% CI=0.512-1.463, p=4.7x10(-5)). Stratification by ethnicity showed significantly elevated prolactin levels in the SLE group in Asian, Latin American, and mixed populations (SMD=0.813, 95% CI=0.137-1.490, p=0.018; SMD=0.981, 95% CI=0.307-1.655, p=0.004; SMD=1.469, 95% CI=0.443-2.495, p=0.005, respectively), but not in the European population. Subgroup analysis by sample size showed significantly higher prolactin levels in the SLE group by small (n<30) and large sample numbers (n>30). Meta-analysis of correlation coefficients showed a significantly positive correlation between circulating prolactin level and SLE activity (correlation coefficient=0.379, 95% CI=0.026-0.487, p=4.0x10(-9)). Circulating prolactin levels were positively associated with SLE activity in European, Asian, and mixed populations (SMD=0.532, 95% CI=0.443-0.609p<1.0x10(-8); SMD=0.427, 95% CI=0.240-0.583, p=2.4x10(-5); SMD=0.433, 95% CI=0.212-0.591, p=2.7x10(-5), respectively). Conclusions Our meta-analysis demonstrated that circulating prolactin levels are higher in patients with SLE, and that a significantly positive correlation exists between prolactin levels and SLE activity.