ABSTRACT

The thyroid gland is an endocrine organ located in the anteroinferior part of the neck, composed of two lobes connected by an isthmus. Due to its superficial position, ultrasonography (US) is the most effective imaging modality for its evaluation. The normal thyroid parenchyma appears homogeneous, moderately to highly echogenic, and is surrounded by a thin capsule. Computed tomography and magnetic resonance imaging are mainly used to assess its mediastinal extension and relationship with adjacent structures, and in the evaluation of suspected malignancies. In selected cases, scintigraphy and elastography can provide additional diagnostic information.

Diffuse thyroid diseases include diffuse simple goiter, Graves’ disease, and various forms of thyroiditis. Diffuse simple goiter is characterized by uniform thyroid enlargement with normal vascularity. Graves’ disease is autoimmune in origin; on US, the gland appears enlarged, hypoechoic, and markedly hypervascular (“thyroid inferno”). Acute suppurative thyroiditis is a rare bacterial infection presenting with hypoechoic abscess-like areas on US. Subacute granulomatous (de Quervain) thyroiditis usually follows a viral infection, is painful, and typically demonstrates patchy hypoechoic, hypovascular areas on US. Subacute lymphocytic (silent/postpartum) thyroiditis commonly occurs in the postpartum period and shows diffusely hypoechoic parenchyma without specific Doppler findings. Hashimoto’s thyroiditis, the most common autoimmune thyroid disease, presents as a hypoechoic, heterogeneous, pseudonodular gland with the characteristic “giraffe pattern”. Riedel’s thyroiditis is a rare fibrosing form in which the gland becomes hard and invades surrounding tissues. Drug-induced thyroiditis is most often associated with amiodarone, lithium, and tyrosine kinase inhibitors.