No association of psoriasis with autoimmune thyroiditis

Common autoimmune diseases tend to coexist in the same patients. Few studies have examined the possible association between autoimmune thyroiditis and psoriasis or psoriatic arthritis (PsA), with inconsistent results.

To investigate the prevalence of autoimmune thyroiditis in psoriatic patients with or without PsA, living in an iodine-sufficient area.

We studied prospectively, 114 psoriatic patients with disease duration of 5-38 years, 30 of them with PsA, and 286 age- and body mass index (BMI)-matched subjects without psoriasis or known thyroid disease or autoimmune disease. A detailed medical history was obtained from all participants and clinical examination and laboratory evaluation was performed. Psoriasis severity was assessed with Psoriasis Area and Severity Index (PASI). Autoimmune thyroiditis was defined by the presence of positive autoantibodies to thyroid peroxidase and/or thyroglobulin.

There was no difference in the prevalence of autoimmune thyroiditis between psoriatic patients and controls (20.2% vs. 19.6%). The prevalence of autoimmune thyroiditis in male and female psoriatic patients was similar (9.6% and 10.5% respectively), in contrast to the increased, as expected, prevalence in female vs. male controls (14.7% vs. 4.9%, P < 0.01). Detected cases with hypothyroidism due to autoimmune thyroiditis were similar in psoriatic patients and controls (7.9% and 7.0% respectively). Autoimmune thyroiditis in psoriatic patients was not related with age of psoriasis onset, psoriasis duration, PASI score, PsA and obesity.

These data support that psoriatic patients with or without PsA do not have an increased risk for autoimmune thyroiditis.