From the Guidelines
The best scan to evaluate hyperthyroidism is an ultrasound (US), as it is the best imaging study to evaluate thyroid morphology and can be a helpful adjunct study to a radioiodine uptake scan. According to the American College of Radiology [ 1 ], US can confirm the presence of nodules and evaluate for suspicious features of malignancy. Additionally, Doppler US may be an alternative to nuclear medicine for separating thyrotoxicosis that is due to an overactive thyroid, such as Graves disease and toxic adenoma, from thyrotoxicosis, which is due to destructive causes such as subacute or lymphocytic thyroiditis.
Some key points to consider when evaluating hyperthyroidism include:
- Measuring thyroid-stimulating hormone (TSH) and free thyroid hormones (T4 and T3) to confirm hyperthyroidism
- Additional testing, such as thyroid antibodies (TSI or TRAb for Graves' disease, anti-TPO for autoimmune thyroiditis), and thyroid imaging (ultrasound and/or radioactive iodine uptake scan) to determine the underlying cause
- Treatment options, including antithyroid medications, radioactive iodine ablation, or thyroidectomy, depending on the cause, patient age, comorbidities, and preferences
- Regular monitoring of thyroid function tests to adjust medication dosing and assess treatment response
It's worth noting that the evidence from [ 1 ] is the most recent and highest quality study, and it provides the most direct evidence on the best scan to evaluate hyperthyroidism. The other studies [ 1, 1, 1, 1, 1, 1, 1, 1 ] provide additional information on the diagnosis and treatment of hyperthyroidism, but they do not provide the same level of evidence as [ 1 ] on the best scan to evaluate hyperthyroidism.
From the FDA Drug Label
Thyroid function tests should be monitored periodically during therapy The best diagnostic approach for hyperthyroidism is to monitor thyroid function tests periodically during therapy.
- Thyroid function tests are the primary method for evaluating hyperthyroidism. There is no information about the best scan to evaluate hyperthyroidism in the provided drug labels 2 2.
From the Research
Diagnostic Approaches for Hyperthyroidism
- The radioactive iodine uptake test is used to identify the cause of hyperthyroidism and to aid in the selection of the I-131 dose in the treatment of hyperthyroidism 3.
- Thyroid scintiscanning is used in the identification of normal and ectopic thyroid tissue, in the diagnosis of the cause of a patient's hyperthyroidism, and as part of the evaluation of selected patients with thyroid nodules 3.
- Pinhole thyroid imaging and 24-h radioactive iodine uptake (RAIU) measurements are also used to evaluate hyperthyroidism 4.
Treatment of Hyperthyroidism
- Radioactive iodine treatment is an effective treatment for Graves' hyperthyroidism, with a success rate of 93.3% in one study 4.
- The goal of RAI treatment is to achieve hypothyroidism within 3-6 months of 131I administration 4.
- Ablative approaches using radioiodine are increasingly proposed for the treatment of Graves' disease, but their ophthalmologic and biological autoimmune responses remain controversial 5.
- Radioiodine thyroid ablation is effective in eradicating Graves' hyperthyroidism, but may be accompanied by Graves' ophthalmopathy occurrence, particularly in patients with early hypothyroidism and high pretreatment TSH-receptor antibodies and/or antithyroid drugs intolerance 5.
Sonographic Features After Radioiodine Therapy
- The typical sonographic features of the thyroid gland in patients with Graves' hyperthyroidism after radioiodine therapy include a significantly reduced mean total volume, hypovascularity, coarse echotexture, and hyperechogenicity 6.
- The mean volumes of the right and left lobes of the thyroid gland are reduced after radioiodine therapy, with a mean total volume of 4.2 mL 6.
Special Considerations
- Thyrotoxicosis with low radioactive iodine uptake has different causes and treatment approaches than hyperthyroidism due to Graves' disease or toxic nodular goiter 7.
- Iodine-induced hyperthyroidism and amiodarone-associated hyperthyroidism may be associated with low radioiodine uptakes and require special consideration 7.