Background <p>It has been hypothesized that an imbalance between thyroid hormones and dopaminergic activity may contribute to the development of Restless legs syndrome (RLS). This study aimed to evaluate the incidence and severity of RLS in patients with Hashimoto’s thyroiditis compared to healthy controls, with a focus on the potential impact of thyroid hormone replacement therapy.</p> Methods <p>A total of 120 consecutive patients, 80 with Hashimoto’s thyroiditis (40 untreated, 40 under treatment) and 40 healthy controls, were included in the study. RLS symptoms were assessed based on the International Restless Legs Syndrome Study Group (IRLSSG) diagnostic criteria. Symptom severity was evaluated using the Restless Legs Syndrome Severity Rating Scale (RLS-SRS).</p> Results <p>RLS symptoms and RLS-SRS scores were significantly higher in patients with Hashimoto’s thyroiditis compared to healthy controls (<i>p</i> &lt; 0.01). The untreated group showed a significantly higher RLS incidence and symptom severity than both the treated group and controls (<i>p</i> &lt; 0.001). No significant difference was observed between the treated Hashimoto’s group and the control group. Additionally, RLS severity was associated with a longer duration of Hashimoto’s disease (<i>p</i> = 0.03).</p> Conclusion <p>The results of our study suggest that RLS is more prevalent and severe in patients with untreated Hashimoto’s thyroiditis. Furthermore, thyroid hormone replacement therapy may have a protective role in reducing both the incidence and severity of RLS in this population.</p>