Abstract: The aetiopathogenesis of hidradenitis suppurativa (HS) is not fully understood; however, increasing evidence suggests that it may be an immune-mediated disorder. Autoimmune thyroid disease (AITD) has classically been considered as the 'paradigm' of autoimmunity, and it has been linked to a variety of skin disorders. To our knowledge, the prevalence of AITD has not been investigated in patients with HS. The aim of the present study was to assess and compare, for the first time, the prevalence of thyroid autoimmunity in 70 patients with HS and in 70 age- and sex-matched controls. In all participants, thyroid autoantibodies and thyroid function tests were analysed. No statistically significant difference was detected between patients with HS and controls, either for the prevalence of thyroid antibodies or for thyroid function parameters. This lack of an association between HS and thyroid autoimmunity suggests that conventional autoimmune mechanisms may not be implicated in the pathogenesis of HS.