Thyroid Stiffness Drops Rapidly in Both Classical and Atypical Subacute Thyroiditis

Thyroid stiffness measured by shear-wave elastography decreases markedly during recovery in patients with subacute thyroiditis, with the steepest decline occurring within the first month after diagnosis across both classical and clinically atypical presentations. In a longitudinal assessment tracking tissue stiffness over six months, researchers observed substantial initial elevations at diagnosis that progressively resolved over time in both disease phenotypes, although between-group differences narrowed significantly across subsequent evaluations.

Clinically atypical subacute thyroiditis poses diagnostic challenges because it often presents with limited symptoms and focal ultrasound abnormalities capable of mimicking suspicious thyroid nodules. While conventional presentations typically feature prominent symptoms, the longitudinal evolution of tissue stiffness in paucisymptomatic atypical cases has remained poorly characterized compared to classical forms of the inflammatory disorder.

To investigate these dynamics, investigators conducted a retrospective, single-center longitudinal cohort study analyzing 92 patients with active subacute thyroiditis diagnosed between January 2020 and January 2026. The study cohort comprised 22 patients presenting with clinically atypical subacute thyroiditis and 70 patients diagnosed with classical subacute thyroiditis, with all included participants having complete shear-wave elastography measurements across four scheduled observation points at baseline, 1 month, 3 months, and 6 months.

Comparative baseline assessments revealed distinct demographic and sonographic differences between the two patient groups at initial presentation. Patients diagnosed with the atypical phenotype were significantly younger than those presenting with classical subacute thyroiditis, with a median age of 37.5 years compared to 45.0 years. Furthermore, bilateral ultrasound involvement occurred less frequently among atypical cases, appearing in 54.5 percent of atypical patients versus 78.6 percent of those with classical disease.

Serial shear-wave elastography demonstrated lower median stiffness values in the atypical group at 1 month, measuring 37.8 kilopascals compared to 46.3 kilopascals in the classical group, and at 3 months, recording 18.4 kilopascals versus 23.0 kilopascals. While both time points were significant under Holm adjustment, only the 1-month difference remained significant following Bonferroni correction. Unadjusted repeated-measures analysis confirmed significant phenotype, time, and phenotype-by-time effects, yet after adjusting for patient age and baseline free thyroxine levels, only the 1-month group difference remained statistically significant after Holm correction, showing a 25.8 percent reduction.

In multivariable regression models examining contributing factors, patient age was significantly associated with baseline stiffness, while baseline stiffness and age both correlated with stiffness at 3 months. The atypical phenotype itself was not independently associated with shear-wave elastography values in either multivariable model. The investigators concluded that although serial elastography effectively documents the resolution of thyroid stiffness during disease recovery, its added clinical value beyond conventional ultrasound, laboratory testing, and clinical assessment remains to be established.

Subject of Research: Longitudinal shear-wave elastography assessment in classical versus clinically atypical subacute thyroiditis

Article Title: Comparative and longitudinal assessment of shear-wave elastography in subacute thyroiditis: classical versus clinically atypical subacute thyroiditis phenotypes

Article References: Bunceanu, S., Bena, A., Neagoe, O. C., Pui, R., Streinu, D. R., Latia, M., & Stoian, D. (2026). Comparative and longitudinal assessment of shear-wave elastography in subacute thyroiditis: classical versus clinically atypical subacute thyroiditis phenotypes. Frontiers in Endocrinology, 17, Article 1979419. https://doi.org/10.3389/fendo.2026.1979419

Image Credits: AI Generated

DOI: 10.3389/fendo.2026.1979419

Keywords: subacute thyroiditis, clinically atypical subacute thyroiditis, shear-wave elastography, thyroid stiffness, ultrasonography, elastic modulus, elasticity imaging techniques, thyroid gland, free thyroxine, retrospective cohort study, longitudinal follow-up, repeated-measures analysis, multivariable regression, thyroid nodules, paucisymptomatic presentation, bilateral ultrasound involvement, tissue stiffness resolution