Allergic rhinitis and its relationship with autoimmune thyroid diseases

Autoimmune thyroid diseases are the most common of all autoimmune diseases. In the literature, Hashimoto thyroiditis (HT) is considered to be a T-helper (Th) type 1 dominant condition, and Graves disease is considered a Th2-dominant condition.

The aim of this study was to highlight a new aspect of the relationships among Th cell subgroups by determining the incidence of autoimmune thyroid disease in patients with allergic rhinitis (AR).

Patients were diagnosed with AR based on their medical histories, physical examinations, and skin-prick test results in an outpatient clinic. The levels of free triiodothyronine, free thyroxine, thyroid-stimulating hormone, thyroid peroxidase antibodies, and thyroglobulin antibodies were measured in peripheral blood samples from all study subjects.

A total of 1239 patients with AR and 700 consecutive, age- and sex-matched healthy subjects were included in the study. Thyroid function tests showed that 1037 patients with AR (83.7%) had normal thyroid function, 171 (13.8%) had euthyroid HT, and 31 (2.5%) had hypothyroid HT. Among the control subjects, thyroid function test results showed that 688 subjects (98.2%) had normal thyroid function, 10 subjects (1.4%) had euthyroid HT, and 2 subjects(0.4%) had hypothyroid HT.

The incidence of HT in the general population is 1.5%; in contrast, it was observed in 16.3% of our patients with AR, which represented a much higher rate than that in the overall population. Graves disease was not detected in our study subjects. A high incidence of HT in patients with AR, in which Th2 responses are dominant, indicates that further studies of the relationships among atopy, autoimmune diseases, and Th cell subgroups are needed.