What is the workup for hyperthyroidism (excessive thyroid hormone production)?

From the Guidelines

The workup for hyperthyroidism begins with measuring thyroid function tests, specifically TSH (which will be suppressed) and free T4 and T3 levels (which will be elevated), as recommended by the American Diabetes Association 1. The initial step in evaluating hyperthyroidism is to assess thyroid function through laboratory tests.

• Measuring TSH levels is the first line of testing, as it will be suppressed in cases of hyperthyroidism.
• If TSH levels are abnormal, free T4 and total T3 measurements can be obtained to confirm the diagnosis.
• Additional tests, such as thyroid autoantibodies (TSI and TRAb for Graves' disease), radioactive iodine uptake scan, and thyroid ultrasound, can help determine the underlying cause of hyperthyroidism.
• Complete blood count and liver function tests should be obtained as baseline measurements before initiating treatment. For symptomatic patients, beta-blockers like propranolol (10-40 mg every 6 hours) or longer-acting metoprolol (25-100 mg twice daily) can provide relief from palpitations, tremors, and anxiety while definitive treatment is being arranged, as discussed in the context of thyrotoxicosis and hyperthyroidism 1. Definitive treatment options include antithyroid medications, radioactive iodine ablation, or thyroidectomy, with the choice depending on the underlying cause, patient age, comorbidities, and preferences. Regular monitoring of thyroid function tests is necessary during treatment, typically every 4-6 weeks initially, then every 3 months once stable. Patients should be educated about symptoms of hypothyroidism or worsening hyperthyroidism that warrant medical attention.

From the Research

Diagnosis of Hyperthyroidism

The diagnosis of hyperthyroidism typically involves a combination of clinical evaluation and biochemical tests, including:

• Low TSH levels
• High free thyroxine (FT4) or high free tri-iodothyonine (FT3) levels 2, 3, 4, 5, 6
• Measurement of thyrotropin receptor autoantibodies to diagnose Graves' disease 3
• Radioiodine uptake scan to distinguish among possible causes of hyperthyroidism 3, 4, 5

Diagnostic Tools

Helpful tools in the diagnosis of hyperthyroidism include:

• Thyroid ultrasonography 2
• Scintigraphy 2
• TSH-receptor antibodies 2
• Thyroid peroxidase antibodies 2

Causes of Hyperthyroidism

The most common causes of hyperthyroidism are:

• Graves' disease (70%) 2
• Toxic nodular goitre (16%) 2
• Subacute granulomatous thyroiditis (3%) 2
• Drugs (9%) such as amiodarone, tyrosine kinase inhibitors, and immune checkpoint inhibitors 2

Treatment Options

Treatment options for hyperthyroidism include:

• Antithyroid drugs (e.g. propylthiouracil, methimazole) 2, 4, 5, 6
• Radioactive iodine (131I) 2, 4, 5
• Thyroidectomy 2, 4, 5
• Radiofrequency ablation (rarely used) 2