Chronic spontaneous urticaria (CSU) is linked to thyroid disease in up to 54%, with predominance of hypothyroidism.To describe the impairments of the thyroid function in patients with CSU in a third level of care.A cross-sectional, observational, and descriptive study in which we have included men and women over 18-year-old with CSU; in which TSH and free T4 were quantified. According to the results, they were classified as euthyroid, hyperthyroid, and hypothyroid; in the latter ones, the presence of antithyroid antibodies was intentionally sought. The demographic and biochemical characteristics of the results were assessed.The clinical characteristics of 127 patients with CSU were analyzed. Women accounted for 78%. The average age was 44.5 ± 15.1 years. Impairments of the thyroid function were identified in 50 patients (39%), and subclinical hypothyroidism (SH) occurred in 41 (82%) of them; patients with hyperthyroidism were not found. Of the patients with hypothyroidism, 14 (28%) presented positive antibodies; all of them were women.More than a third of the analyzed patients with CSU presented impairments of the thyroid function; subclinical hypothyroidism (SH) was more common. The importance of identifying this entity lies in the possibility of a multidisciplinary treatment with endocrinology. Subsequent studies may establish whether the presence of hypothyroidism influences the activity of CSU.