Background: Rheumatoid arthritis (RA) and ankylosing spondylitis (AS) are chronic autoimmune inflammatory disorders in which TNF-α plays a key role. Anti-TNF agents are widely used in the management of these diseases.
Objective: Since TNF-α is also involved in the pathogenesis of autoimmune thyroid disease (AITD), this study aimed to assess whether anti-TNF therapy influences thyroid function.
Methods: This prospective study included 50 RA and 51 AS patients aged 18–85 years. Patients received either conventional treatment (DMARDs and NSAIDs/sulfasalazine) or anti-TNF agents. Serum TSH, free T4, and anti-TPO levels were measured at baseline and after 6 months. Thyroid dysfunction and AITD prevalence were compared between the two treatment groups.
Results: In the RA group, subclinical hyperthyroidism was observed in both arms; in the anti-TNF group, one patient had hypothyroidism, and another had subclinical hypothyroidism. Improvement in subclinical hyperthyroidism was observed in one patient in the DMARD arm, in one patient with hypothyroidism, and in one patient with subclinical hyperthyroidism in the anti-TNF arm (p>0.05). In the AS group, central hyperthyroidism developed in one patient receiving conventional treatment. In the anti-TNF group, one patient with subclinical hypothyroidism improved to normal values, while another developed central hypothyroidism. Anti-TPO positivity was 18% in the conventional group and 3.4% in the anti-TNF group (p>0.05). A significant TSH change was observed only in the RA-DMARD group (p < 0.05), while no significant changes in free T4 were detected in any group.
Conclusion: Anti-TNF therapy showed no significant effect on thyroid function or autoimmune thyroid disease in patients with RA and AS during a six-month follow-up.