Is a thyroid ultrasound recommended after diagnosis of Graves' disease?

Thyroid Ultrasound in Graves' Disease

Thyroid ultrasound should be performed after diagnosis of Graves' disease to detect nodules that may coexist with thyroid hyperplasia, as these nodules have a significant risk of malignancy and are often missed on clinical examination. 1

Rationale for Thyroid Ultrasound in Graves' Disease

Clinical Limitations and Nodule Detection

• Clinical examination alone is insufficient for detecting thyroid nodules in Graves' disease patients
• In a study of patients with Graves' disease, 45% had significant nodularity on ultrasound, but only 67% of these nodules were identified on clinical examination 1
• Ultrasound is significantly more sensitive than scintigraphy in detecting thyroid nodules (16% vs 2.1%, p<0.001) 2

Malignancy Risk

• The prevalence of thyroid cancer in Graves' disease patients is at least 3.3%, with most being micropapillary thyroid cancers 3
• In one study, thyroid cancer was diagnosed in 47.7% of Graves' disease patients with solid nodules detected by ultrasound 2
• Patients aged 45 years or older are more likely to harbor locally advanced thyroid cancers regardless of hyperthyroidism duration, severity, goiter size, or antibody activity 3

Cost-Effectiveness Considerations

• Ultrasound is more cost-effective than scintigraphy as the first diagnostic procedure in hyperthyroid patients 2
• Total cost for diagnosis by ultrasound was €14,645.34 versus €19,922.71 by scintigraphy in one study 2
• Using ultrasound first reduces the direct cost of nodule management compared to starting with scintigraphy 2

Diagnostic Algorithm for Graves' Disease

1. Initial Diagnosis:

   • Measure TSH, Free T3, and Free T4 to confirm hyperthyroidism 4
   • Perform thyroid ultrasound to evaluate thyroid morphology, nodularity, and vascularity 4

2. For Hyperthyroidism Confirmation:

   • Nuclear thyroid uptake study is recommended to directly measure thyroid activity and differentiate between various causes of thyrotoxicosis 4
   • Doppler ultrasound may be an alternative to nuclear medicine for separating thyrotoxicosis due to an overactive thyroid from thyrotoxicosis due to destructive causes 5

3. For Nodule Management:

   • Fine-needle aspiration (FNA) for nodules ≥5mm 3 or ≥8mm 6
   • Follow-up ultrasound annually to monitor for new nodule development 6

Important Caveats and Considerations

• Malignant nodules in Graves' disease may present with blurred margins, microcalcifications, and an anteroposterior/transverse diameter ratio ≥1 2
• Most thyroid cancers in Graves' disease are detected only by ultrasound and not by palpation 3
• When FNA cytology does not indicate malignancy, the presence of thyroid nodules in patients with Graves' disease does not necessarily indicate an aggressive therapeutic approach 6
• After radioiodine therapy for Graves' disease, typical sonographic features include reduced thyroid volume, hypovascularity, coarse echotexture, and hyperechogenicity 7

In conclusion, while the American College of Radiology does not specifically address ultrasound for Graves' disease in its appropriateness criteria 5, the evidence strongly supports performing thyroid ultrasound after diagnosis of Graves' disease due to the high prevalence of nodules that may harbor malignancy and are frequently missed on clinical examination.