High prevalence of thyroid autoimmunity and hypothyroidism in patients with psoriatic arthritis

OBJECTIVE:To evaluate the prevalence of thyroid disorders in a group of patients with psoriatic arthritis (PsA). METHODS:A complete thyroid investigation was carried out in 80 patients with PsA, in gender- and age-matched subjects (1:5) drawn from the general population (controls), and in 112 patients with rheumatoid arthrtitis (RA) with similar iodine intake. RESULTS:Anti-thyroid peroxidase antibodies (AbTPO), a hypoechoic thyroid, and subclinical hypothyroidism were significantly more frequent in women with PsA than in control women, and their frequency was similar to that in patients with RA (positive AbTPO titer 28%, 12%, and 31%; hypoechoic thyroid 31%, 16%, and 36%; subclinical hypothyroidism 25%, 8%, and 12%, respectively). Among men, positive AbTPO titers and a hypoechoic thyroid were found more frequently in the patients with PsA and RA than in controls (positive AbTPO titer 14%, 5%, and 2%; hypoechoic thyroid 16%, 10%, and 3%, respectively). All patients with PsA with subclinical hypothyroidism had polyarticular involvement (p </= 0.05) and a longer disease duration (years 19 +/- 15 vs 11 +/- 8, p = 0.03) than patients with euthyroid PsA. The prevalence of subclinical hyperthyroidism, thyroid nodules, and thyroid enlargement was not significantly different among the 3 groups. CONCLUSION:Our results demonstrate a significantly higher prevalence of thyroid autoimmunity (positive AbTPO, hyoechoic thyroid) findings in men and women with PsA and of subclinical hypothyroidism in women with PsA than in the general population. Therefore, thyroid function tests, an AbTPO assay, and thyroid ultrasound should be performed as part of the clinical evaluation, particularly in women with PsA.