Melasma and thyroid disorders: a systematic review and meta‐analysis

Abstracts Background Thyroid hormones may play a key role in melasma; however, melasma link with thyroid disorders remains controversial. Objectives To compare the serum levels of thyroid‐stimulating hormone (TSH), T4, T3, anti‐thyroid peroxidase (anti‐TPO), and antithyroglobulin between patients with melasma and control group using meta‐analysis. Methods We screened 10 databanks and search engines, searched mesh and nonmesh terms. The identified evidences were reviewed and quality assessed using the Newcastle‐Ottawa Scale (NOS). The heterogeneity between the primary results was investigated using Cochrane and I ‐square indices. Random effect model was applied to combine the standardized mean differences of thyroid function indicators between patients with and without melasma. P values meta‐analysis was used to investigate the association between anti‐TPO and melasma. Results We included seven studies, 473 cases, and 379 controls that had been investigated. The total standardized mean differences (95% confidence intervals) of TSH, T3, T4, and antithyroglobulin antibody between cases and controls were estimated to be 0.33 (0.18, 0.47), −0.01 (−0.20, 0.19), −1.50 (−2.96, −0.04), and 0.62 (0.14, 1.11), respectively. The corresponding figures among women were 0.35 (0.17, 0.52), 0.10 (−0.17, 0.38), −2.75 (−6.30, 0.81), and 0.99 (0.14, 1.83), respectively. P value of meta‐analysis showed a significant relationship between anti‐TPO serum level and melasma (Fisher = 26.80, P  = 0.020). Conclusion Serum levels of TSH, anti‐TPO, and antithyroglobulin antibody were significantly higher in patients with melasma than those without melasma. Moreover, these differences were more severe among women with melasma.