Increased thyroid stiffness without volume change in systemic sclerosis: a case-control study using two-dimensional shear wave elastography.

Elastographic data regarding thyroid involvement in systemic sclerosis (SSc) are limited. This study aimed to evaluate thyroid parenchymal stiffness in patients with SSc using two-dimensional shear wave elastography (2D-SWE) and to investigate its relationship with clinical parameters. This single-center, cross-sectional case-control study included 36 SSc patients and 36 age- and gender-matched healthy controls. All participants underwent thyroid ultrasonography and 2D-SWE. Thyroid volume was calculated using the ellipsoid formula, and elasticity values were recorded in kilopascals (kPa). Clinical characteristics, laboratory parameters, and disease severity indices were recorded, and correlation analyses were performed. Thyroid volume and isthmus thickness were similar between groups (all p > 0.05; d = 0.10-0.35). Right, left, and total thyroid elasticity values were significantly higher in SSc patients than in controls before and after smoking adjustment (all unadjusted p ≤ 0.001; all adjusted p ≤ 0.007; d = 0.83, 0.79, and 0.90, respectively). Right lobe elasticity correlated weakly with erythrocyte sedimentation rate (r = 0.355; p = 0.034), while left and total thyroid elasticity correlated moderately with ejection fraction (r = 0.423; p = 0.010 and r = 0.390; p = 0.019, respectively). No significant associations were found with disease duration, modified Rodnan skin score, EUSTAR Activity Index, Medsger Disease Severity Score, autoantibody status, or major organ involvement. In SSc, thyroid parenchymal stiffness increases without volume change. This suggests that the fibrotic process may be reflected in the thyroid tissue at a subclinical level. Thyroid elastography may be a potential method for evaluating organ-specific fibrotic changes in SSc; further large-scale and prospective studies are needed to clarify its clinical significance.