Association between lichen sclerosus and thyroid diseases: A systematic review and meta-analysis

Background Lichen sclerosus (LS) is a chronic inflammatory dermatosis characterised by ivory-white patches to plaques. Evidence suggests an autoimmune aetiology for LS, given its association with various autoimmune conditions, such as autoimmune thyroiditis, alopecia areata (AA), and vitiligo. However, the association between LS and thyroid diseases remained controversial. Aim We aimed to investigate the association between LS and thyroid diseases. Methods We performed a systematic review of studies on the association between LS and thyroid diseases. We searched CENTRAL, MEDLINE, and Embase from inception to May 28, 2024. Studies were included if they were case-control designs with LS patients and controls, reported thyroid disease outcomes, and provided effect estimates; two authors screened titles and abstracts to exclude studies without LS or thyroid data, lacking controls, reviews, case reports, or grey literature, with disagreements resolved by the corresponding author. Odds ratio (OR) of various thyroid conditions in relation to LS was calculated using a random-effects model meta-analysis. When adjusted estimates were available, the pooled adjusted OR (aOR) was calculated. The risk of bias in the selected studies was assessed using the Newcastle-Ottawa Scale for case-control studies. Results We included nine studies involving 1,77,488 LS patients and 2,21,77,269 controls. Most patients, primarily middle-aged females, were recruited from USA, and others were recruited from Poland, Sweden, UK, Finland, and Serbia. All the studies scored 7 or higher for quality in selection, comparability, and exposure. Significant associations were identified between LS and various thyroid conditions, including thyroid diseases (OR 2.48; 95% confidence interval (CI) 2.01-3.05, from two studies, 1,055 LS patients and 2,040 controls), thyroiditis (OR 2.07; 95% CI 1.18-3.63, from two studies, 1,202 LS patients and 2,252 controls), autoimmune thyroid disease (OR 4.07; 95% CI 3.78-4.38, from one study, 10,004 LS patients and 21,672,016 controls), autoimmune thyroiditis/Hashimoto thyroiditis (OR 2.97; 95% CI 1.92-4.59, from three studies, 21,461 LS patients and 21,707,152 controls), and Graves' disease (OR 2.34; 95% CI 2.02-2.71, from 1 study, 10,004 LS patients and 21,672,016 controls) based on crude estimates. The adjusted estimates revealed significantly increased odds of family history of thyroid disease (aOR 9.10; 95% CI 2.30-36.00), hypothyroidism (aOR 1.91; 95% CI 1.24-2.95), thyroiditis (aOR 2.00; 95% CI 1.22-3.29), and autoimmune thyroiditis/Hashimoto thyroiditis (aOR 2.88; 95% CI 1.95-4.25) among LS patients. Limitations Limitations such as a small number of included studies, lack of subgroup data, reliance on a few studies for analysis, absence of long-term cohort data, potential influence of systemic treatments, and variability in thyroid disease terminology highlight the need for future research with more diverse populations, standardised definitions, and comprehensive data. Significant association exists between LS and thyroid diseases, particularly thyroiditis and autoimmune thyroiditis/Hashimoto thyroiditis. The physicians should look for thyroid related symptoms, such as, palpitation, heat intolerance, and body weight changes in LS patients, and early endocrinology consult should be sought to diagnose and manage thyroid diseases. Conclusion We found significant associations between LS and thyroid diseases, particularly thyroiditis and autoimmune thyroiditis, as well as Hashimoto thyroiditis.