Thyroid-specific changes following treatment with biological therapies in patients with rheumatic diseases

Biological anti-rheumatic agents (BAA) may induce autoimmune phenomena. Evidence on thyroid-specific effects of these agents is relatively limited. We studied prospectively, over 3 years, 36 rheumatic patients treated with BAA (18 Infliximab and 18 Rituximab) and no prior exposure to biological therapies (group-1), with respect to their thyroid function, thyroid antibody titers, and thyroid ultrasonographic parameters, such as left inferior thyroid artery peak systolic velocity (ITA PSV), left thyroid lobe vascularity index (TL VI), and echogenicity. Twenty-eight rheumatic patients treated with disease-modifying anti-rheumatic drugs and/or glucocorticoids (group-2), 21 rheumatic patients not receiving any treatment (group-3), and 49 healthy individuals (group-4) were used for comparison. Thyroid function and autoantibody titers were not significantly altered at any stage irrespectively of the administered BAA, previously unknown autoimmune thyroid disease (AITD) status, and/or concomitant treatment with glucocorticoids. Left ITA PSV was significantly increased in group-1 patients (mean ± SD start: 25.5 ± 14.1 cm/s vs. end: 29.8 ± 11.1 cm/s, p = 0.038 and p < 0.001, respectively). Six group-1, 7 group-2, and 3 group-3 patients developed reduced thyroid echogenicity during follow-up (start: p = 0.003 and end: p < 0.001). Left ITA PSV, left TL VI, and echogenicity changes were not related to alterations in thyroid volume, thyrotropin hormone levels, and/or underlying AITD. Infliximab and Rituximab do not cause any alterations in thyroid function and/or autoimmunity, even in patients with previously undiagnosed AITD. Elevated left ITA PSV and reduced thyroid echogenicity may be early features signaling progression to AITD in patients treated with BAA.