**2.1. Introduction**

Alopecia areata (AA) is a clinical condition characterized by well circumscribed, round, or oval patches of hair loss on the scalp or other parts of the body. Sometimes, alopecia totalis (AT), loss of all scalp hair, or alopacia universalis (AU), loss of all body hair, may develop. This disorder affects both sexes equally and occurs at all ages, although children and young adults are affected most often. The etiopathogenesis of AA is still unclear, but there is evidence that autoimmunity and endocrine dysfunction may be involved [24-26]. The autoimmune etiology has been proposed on the basis of its association with various autoimmune diseases, the presence of autoantibodies and various underlying immune abnormalities in the affected sites of these patients [27, 28]. One of the main associations is with thyroid abnormalities. This association was further supported by an increased incidence of abnormal thyroid structure, function tests and/or presence of thyroid autoantibodies found in many studies [29-32].

The aim of this study was to determine the prevalence of thyroid autoimmunity in patients with AA.

### **2.2. Patients and methods**

The study included 70 patients with AA (40 female and 30 male). A detailed history and examination were taken in all study subjects, including patients age, age at onset, duration of disease, associated diseases, history of thyroid disorders and the extent and severity of disease. The diagnosis of AA was made on clinical grounds. Skin biopsy was performed in selected cases. No patient was diagnosed before this study as having any type of thyroid dysfunction. The control group consisted of 70 volunteers (40 female and 30 male) who had skin diseases other then AA or autoimmune disorders. Blood samples were taken and a physical examination and thyroid sonography was performed. All subjects gave their informed consent in accordance with the requirements of the institutional Ethichs Committee. Thyroid autoantibodies (thyroglobulin antibody, anti-Tg, and thyroid peroxidase antibody, anti-TPO) and thyroid hormones (thyroxine (T4), triiodthyronine (T3) and thyroid stimulating hormone (TSH) were measured in all subjects. Total T4 (normal range: 70-180 nmol/L) and total T3 (normal range: 1.3-3.3 nmol/L) were measured by use of radioimmunoassay (RIA); TSH (normal range: 0.3-4.2 mlU/L) was determined by use of immunoradiometric assay (IRMA) (BRAHMS Aktiengesellshaft, Hennigsdorf, Germany). Serum levels of anti-Tg (threshold value: 115 IU/mL) and anti-TPO (borderline value: 34 IU/mL) were measured by use of electrochemiluminiscence immunoassay (ECLIA) according to standard protocols (COBAS, Roche Diagnostics GmbH, Mannheim, Germany).

Baseline clinical characteristics for the two groups were compared with the use of Student's t-test for continuous variables, the chi-square test or Fisher's exact test (two-sided) for categorical variables, as appropriate. Data were considered statistically significant at P <0.05.

Statistical analyses were performed using MedCale for Windows, version 11.4.1.0 (MedCale Software, Mariakerke, Belgium).
