What is the role of ultrasound in a hypothyroidism (underactive thyroid) patient with goitre (enlarged thyroid gland)?

Role of Ultrasound in Hypothyroidism with Goitre

There is no role for ultrasound imaging in the workup of hypothyroidism in adults, even when a goitre is present, as imaging for thyroid morphology does not help differentiate among causes of hypothyroidism or alter management. 1

Guideline-Based Recommendation

The American College of Radiology (ACR) Appropriateness Criteria explicitly states that ultrasound has no utility in evaluating primary hypothyroidism in adults. 1 This recommendation applies regardless of whether the patient presents with thyroid enlargement (goitre), because:

• Imaging cannot differentiate between causes of hypothyroidism (Hashimoto thyroiditis, iodine deficiency, post-ablation, medication-induced, etc.). 1
• All causes of hypothyroidism demonstrate decreased radioiodine uptake, making functional imaging equally unhelpful. 1
• Treatment is thyroid hormone replacement regardless of the underlying etiology or gland morphology. 1

When Ultrasound IS Indicated in Goitre

The key distinction is that ultrasound plays a role in evaluating goitre itself (as a separate clinical entity), but NOT in evaluating the hypothyroidism. 1, 2

Ultrasound should be performed when:

• A goitre presents with obstructive symptoms (dyspnea, orthopnea, dysphagia, dysphonia) to document size, extent, and degree of tracheal or esophageal compression for surgical planning. 1
• Discrete thyroid nodules are palpable within the goitre to characterize malignancy risk using standardized criteria (ACR TI-RADS) and guide fine needle aspiration decisions. 1, 2
• The goitre is suspected to extend substernally, where ultrasound can confirm diagnosis and extent (though CT may be preferred for retrosternal extension). 1

Clinical Algorithm

For a hypothyroid patient with goitre:

1. Measure TSH and treat hypothyroidism with levothyroxine replacement - this is the primary management regardless of imaging findings. 1

2. Perform ultrasound ONLY if:

   • Discrete palpable nodules are present within the goitre (to assess malignancy risk). 1, 2
   • Obstructive symptoms exist (to quantify compression and plan potential surgery). 1
   • There is clinical concern for substernal extension or invasive features. 1

3. Do NOT perform ultrasound if:

   • The patient has diffuse goitre without discrete nodules. 1
   • The goitre is asymptomatic without compressive symptoms. 1
   • The sole purpose is to "evaluate the hypothyroidism" or determine its cause. 1

Common Pitfalls to Avoid

• Do not order ultrasound reflexively just because a goitre is present in a hypothyroid patient - the hypothyroidism diagnosis and management are based on laboratory values (TSH, free T4), not imaging. 1
• Recognize that ultrasound findings in Hashimoto thyroiditis (heterogeneous, hypoechoic texture) are descriptive but do not change management or confirm the diagnosis better than thyroid peroxidase antibodies. 1
• Avoid using ultrasound to "monitor" treated hypothyroidism - thyroid morphology changes do not correlate with treatment adequacy; follow TSH levels instead. 1

Supporting Context from Research

While older literature describes ultrasound characteristics of various thyroid pathologies including goitre 3, 4, and research confirms ultrasound can identify nodules and assess goitre features 2, 5, these capabilities do not translate into clinical utility for hypothyroidism management. The 2019 ACR guidelines supersede earlier practices and provide clear evidence-based direction that imaging adds no value to hypothyroidism workup. 1

The bottom line: Treat the hypothyroidism with hormone replacement based on laboratory values, and reserve ultrasound exclusively for evaluating concerning nodules or symptomatic goitre complications - not for the hypothyroidism itself. 1