Increased incidence of autoimmune thyroid disorders in patients with psoriatic arthritis: a longitudinal follow-up study.

Contrasting results have been reported about the prevalence of thyroid autoimmunity (AT) and dysfunction (TD) in patients with psoriatic arthritis (PsA). In this study, we pointed to evaluate the incidence of new cases of clinical and subclinical TD in a broad group of patients with PsA versus a control group, matched by age and gender belonging to the same geographic area. PsA patients with TD were excluded firstly, and new cases of thyroid disorders were evaluated in 97 PsA patients and 97 matched controls, who had comparable iodine intake (median follow-up of 74 months in PsA versus 92 in controls). A raised rate of new cases of hypothyroidism, TD, positive antithyroid peroxidase (AbTPO) antibodies, and appearance of a small hypoechoic thyroid pattern in PsA, especially in female gender, compared to controls has been evidenced. Risk factors in female gender for the development of TD are thyroid-stimulating hormone (TSH) within the normal range but at the higher limit, positive AbTPO, and small thyroid volume. To sum up, thyroid function follow-up and suitable treatments should be performed regularly in female patients at high risk (TSH within the normal range but at the higher limit, positive AbTPO, hypoechoic and small thyroid).