Thyroid dysfunction in primary Sjögren's syndrome: a long-term followup study.

OBJECTIVE To evaluate the prevalence of thyroid dysfunction and related autoantibodies in patients with primary Sjögren's syndrome (pSS), and to determine whether these abnormalities develop over time. METHODS pSS patients (n = 137) and controls (n = 120) were investigated for thyroid dysfunction and for the presence of anti-thyroid peroxidase antibody (anti-TPO) and antithyroglobulin antibody (ATG). Followup time for patients was 1-16 years, and 72 of the 120 controls were reevaluated 3 years after initial evaluation. RESULTS Thyroid disease was more frequent in the pSS patients than in the controls (30% versus 4%; P < 10(-4)), as were anti-TPO and ATG (11% versus 3%; P < 0.02, and 3% versus 1%, not significant). Ten of 107 euthyroid pSS patients dropped out of the study, and thyroid dysfunction became apparent at followup in 12 of the remaining 97. Most of the patients with thyroid-related autoantibodies at entry developed autoimmune thyroid disease thereafter. CONCLUSION Thyroid dysfunction is frequent in pSS patients, and those prone to develop thyroid disorders are identified by thyroid-related autoantibodies, or by rheumatoid factor and anti-Ro/SSA activity.