“…Evidence also exists that thyroid disease, mainly hypothyroidism, is involved in the pathogenesis of OLP (Garcia‐Pola, Llorente‐Pendas, Seoane‐Romero, Berasaluce, & Garcia‐Martin, ; Lo Muzio, Santarelli, Campisi, Lacaita, & Favia, ; Siponen, Huuskonen, Laara, & Salo, ) and cutaneous lichen planus (Dreiher, Shapiro, & Cohen, ). The serum levels of thyroid antibodies, including antithyroglobulin and antithyroperoxidase antibodies, are increased in patients with OLP (Alikhani et al., ; Chang, Chiang, Hsiao, & Sun, ; Lin, Wang, Chia, & Sun, ). Although the designs of the aforementioned studies do not enable the establishment of causality, it is evident that either the use of LT 4 or an underlying thyroid disorder plays an important role in the aetiology of OLP in a subgroup of patients.…”