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

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.