What is the workup for a patient with an enlarged thyroid gland (goiter)?

Workup for Enlarged Thyroid Gland (Goiter)

The initial workup for a patient with an enlarged thyroid gland should include thyroid function tests (TSH, free T4), thyroid ultrasound, and targeted laboratory tests based on suspected etiology. 1

Initial Evaluation

Laboratory Assessment

1. Thyroid Function Tests:

   • TSH: Primary screening test for thyroid dysfunction 1, 2
   • Free T4: To distinguish between subclinical and overt thyroid dysfunction 3
   • Free T3: Consider if TSH is low but free T4 is normal (to rule out T3 toxicosis) 3

2. Additional Laboratory Tests (based on clinical suspicion):

   • Thyroid antibodies:
     • Anti-TPO and anti-thyroglobulin antibodies (for autoimmune thyroiditis)
     • TSH receptor antibodies (if Graves' disease suspected) 3
   • Calcitonin: If medullary thyroid cancer is suspected 1
   • Thyroglobulin: For monitoring differentiated thyroid cancer 1

Imaging Studies

1. Thyroid Ultrasound:

   • First-line imaging modality for all patients with goiter 1, 4
   • Evaluates:
     • Thyroid size and morphology
     • Presence of nodules and their characteristics
     • Vascularity (using Doppler)
     • Cervical lymphadenopathy 1

2. CT Neck/Chest:

   • Indicated for:
     • Substernal or retrosternal extension
     • Suspected tracheal compression
     • Large goiters with compressive symptoms 1, 5

3. Radioiodine Uptake and Scan:

   • Indicated when:
     • Hyperthyroidism is present (low TSH)
     • Toxic nodular goiter is suspected
     • Need to distinguish between causes of thyrotoxicosis 1, 4
   • Not indicated in hypothyroidism (all causes show decreased uptake) 1

4. Fine Needle Aspiration (FNA):

   • Indicated for:
     • Suspicious nodules identified on ultrasound
     • Dominant nodules in multinodular goiter 6

Diagnostic Algorithm Based on TSH Results

If TSH is Normal (Euthyroid Goiter):

1. Perform thyroid ultrasound to evaluate morphology and nodules
2. If nodules are present, evaluate per nodule guidelines for FNA
3. Assess for compressive symptoms
4. Consider iodine status evaluation in endemic areas 7, 6

If TSH is Low (Hyperthyroid Goiter):

1. Measure free T4 and free T3
2. Perform radioiodine uptake and scan to distinguish between:
   • Graves' disease (diffusely increased uptake)
   • Toxic nodular goiter (focal areas of increased uptake)
   • Thyroiditis (decreased uptake) 1, 3
3. Consider TSH receptor antibodies if Graves' disease is suspected 3

If TSH is High (Hypothyroid Goiter):

1. Measure free T4 to confirm hypothyroidism
2. Test for thyroid antibodies to diagnose Hashimoto's thyroiditis
3. Ultrasound to evaluate for nodules and morphology 1, 4

Special Considerations

Substernal Goiter

• CT or MRI is essential to evaluate extent and compression of vital structures
• Assess airway patency and potential surgical approach 1, 5

Rapidly Growing Goiter

• Urgent evaluation with ultrasound and FNA
• Consider CT/MRI to rule out aggressive malignancy 1

Compressive Symptoms

• Document symptoms (dysphagia, dyspnea, voice changes)
• Consider pulmonary function tests
• Evaluate with CT to assess tracheal compression 1, 5

Common Pitfalls to Avoid

1. Overlooking subclinical thyroid dysfunction: Always check TSH even if patient appears clinically euthyroid 2

2. Missing substernal extension: Patients with seemingly small cervical goiters may have significant intrathoracic extension 5

3. Inappropriate use of radioiodine scans: Not helpful in hypothyroidism or euthyroid states without nodules 1

4. Failure to evaluate nodules: All nodules should be risk-stratified with ultrasound to determine need for FNA 1, 6

5. Overlooking malignancy: Particularly in elderly patients with longstanding goiters that suddenly change in size or symptomatology 1

By following this systematic approach to goiter evaluation, clinicians can efficiently diagnose the underlying cause and determine appropriate management strategies to improve patient outcomes related to morbidity, mortality, and quality of life.