MTNR1B and systemic lupus erythematosus: The results indicated that, in patients with SLE, there was a significant difference of MTN level among genotype of AA, AG, and GG in rs1562444 (MTNR1b) (P = 0.001), which GG genotype showed an elevated MTN concentration than in AA and AG genotype (20.57 pg/ml vs 14.08 pg/ml vs 10.36 pg/ml).