Hashimoto's Thyroiditis: Identifying the Characteristic Ultrasound Pattern

Dr. Segnini
Jan 2
3 min read

Dr. Segnini Hashimoto's thyroiditis ultrasound

When the Immune System Attacks the Thyroid. Hashimoto's thyroiditis ultrasound

Hashimoto's thyroiditis, also known as chronic autoimmune thyroiditis, is the most common cause of hypothyroidism (low thyroid function) worldwide. It is a disease in which the immune system produces antibodies that slowly attack and damage the thyroid gland, leading to chronic inflammation and, ultimately, a decreased ability to produce hormones. Although the diagnosis is confirmed with blood tests (elevated anti-TPO and anti- thyroglobulin antibodies ), thyroid ultrasound plays a crucial role in the initial evaluation, differential diagnosis, and monitoring of the disease.

The Key Role of Ultrasound in Hashimoto's Disease.

Ultrasound does not diagnose thyroiditis on its own, but it provides invaluable anatomical information that complements laboratory findings:

Confirms Clinical Suspicion: A typical Hashimoto's ultrasound pattern in a patient with elevated antibodies confirms the diagnosis.
Evaluate the Extent of Damage: Shows the degree of involvement of the thyroid parenchyma.
Performs Differential Diagnosis: Helps distinguish Hashimoto's from other thyroiditis (such as that of De De Quervain or the silent one) or simple goiter.
Identify Associated Nodules: Patients with Hashimoto's have a slightly increased risk of developing thyroid nodules and certain types of cancer (lymphoma, papillary carcinoma). Ultrasound is the perfect tool for their detection and characterization.
Procedure Guide: Essential for guiding fine needle biopsies (FNAB) of suspicious nodules that may arise in a gland with Hashimoto's disease.

The Classic Ultrasound Pattern: A "Battlescape"

The ultrasound appearance of Hashimoto's thyroiditis is very characteristic, although it can vary in its presentation.

1. Parenchymal Findings (of the Thyroid Tissue):

Diffuse and heterogeneous hypoechogenicity : This is the cardinal and most important sign . The thyroid gland loses its normal echogenicity (which is similar to that of the sternocleidomastoid muscle) and becomes globally darker ( hypoechoic ) . In addition, it presents a heterogeneous or "mottled" texture , like a "honeycomb" or "ground glass," due to lymphocytic infiltration and focal destruction of the follicles.
Hypervascularization on Doppler (Forest Fire Pattern): In the active phases of the disease, especially if there is transient hyperthyroidism ( hashitoxicosis ), the gland may show a marked and diffuse increase in vascularization on color Doppler ultrasound . This pattern of multiple small vessels throughout the gland is often described as "forest fire" ( inferno thyroid ).

2. Structural Findings:

Isthmus thickening: The isthmus (the portion that connects the two lobes) is usually noticeably thickened (>3-4 mm).
Pseudonodular appearance : Extreme heterogeneity of the parenchyma can create the illusion of multiple small nodules, a phenomenon known as pseudonodularity . Distinguishing these pseudonodules from true nodules requires expertise.
Presence of Hyperechoic Streaks : In some cases, fine hyperechoic (bright) lines are observed dividing the hypoechoic parenchyma, corresponding to septal fibrosis .
Glandular Size: The gland may be enlarged (goiter), of normal size, or, in very late stages of the disease (when the tissue is replaced by fibrosis), atrophied and reduced.

3. Associated Lymphatic Findings:

Reactive Lymphadenopathy: Enlarged lymph nodes are commonly found in the cervical region, specifically in the juxtathyroid and jugular chains . These nodes typically have a benign reactive morphotype : oval shape, preserved echogenic central fatty hilum, and a length-to-width ratio (L/W ratio) >2.

Ultrasound Variants and Differential Diagnosis.

Hypertrophic Nodular Form: May coexist with true nodules, which should be evaluated individually according to TI-RADS criteria, since Hashimoto's is a risk factor for neoplasia.
VS. Thyroiditis of De De Quervain (Subacute): In De Quervain , pain on palpation with the transducer is key, and the hypoechogenicity is usually patchy and asymmetric , respecting areas of normal tissue.
Multinodular Goiter : In goiter, the parenchyma between the nodules is usually of normal echogenicity , unlike the diffusely hypoechoic parenchyma of Hashimoto's.

Safety and Monitoring: What to Do with Nodules in a Hashimoto's Gland?

This is a crucial point. The presence of Hashimoto's thyroiditis does not change the criteria for evaluating a nodule . A nodule arising in a thyroid gland with thyroiditis should be analyzed using the same risk criteria (TI-RADS). In fact, some studies suggest that papillary carcinomas in this context may be more aggressive. Therefore, regular ultrasound monitoring and fine-needle aspiration biopsy (FNAB) of suspicious nodules remain essential.

Conclusion: Ultrasound as a Mirror of Inflammation

Thyroid ultrasound is an indispensable tool in the management of Hashimoto's thyroiditis. It provides a non-invasive "virtual biopsy" of the glandular parenchyma, accurately reflecting the ongoing chronic inflammatory process. Its characteristic pattern ( diffuse and heterogeneous hypoechogenicity ) not only supports the diagnosis but also establishes a baseline for comparison in future follow-up visits, evaluates the response to hormone replacement therapy, and, most importantly, actively monitors for the possible development of malignant nodules in an already vulnerable gland. For both the endocrinologist and the patient, it is a valuable tool for long-term management and safety.