What are the appropriate tests and treatment for a patient with a history of goiter and presenting with left arm discomfort?

Evaluation and Management of Goiter with Left Arm Discomfort

The left arm discomfort requires immediate cardiac evaluation to rule out acute coronary syndrome before proceeding with goiter workup, as this symptom is not typically associated with thyroid pathology and may represent a life-threatening cardiac emergency.

Immediate Priority: Cardiac Assessment

• Left arm discomfort is a classic anginal equivalent and must be evaluated urgently with ECG, cardiac biomarkers (troponin), and cardiology consultation to exclude myocardial ischemia or infarction before attributing symptoms to the goiter.
• While goiters can cause compressive symptoms like dyspnea, dysphagia, or dysphonia 1, 2, left arm pain is not a recognized manifestation of thyroid disease and should raise immediate concern for cardiac pathology.
• Only after cardiac causes are excluded should you proceed with thyroid evaluation.

Thyroid Evaluation Algorithm (After Cardiac Clearance)

Step 1: Initial Laboratory Testing

• Measure serum TSH first, as it is the most sensitive initial test with 98% sensitivity and 92% specificity for detecting thyroid dysfunction 3.
• Add free T4 and free T3 to the initial panel, as this directly measures biologically active hormones and is the current standard of care 3.
• TSH results will guide all subsequent imaging decisions 4.

Step 2: Thyroid Ultrasound

• Perform thyroid ultrasound as the initial imaging study for all patients with suspected goiter, regardless of TSH results 1.
• Ultrasound confirms the cervical mass originates from thyroid tissue, characterizes size and morphology, evaluates nodules for malignancy risk using ACR TI-RADS criteria, and identifies suspicious features requiring biopsy 1, 5.
• This is superior to radionuclide scanning in euthyroid patients, which has low diagnostic value and should not be performed routinely 4, 1.

Step 3: TSH-Guided Additional Testing

If TSH is LOW (suppressed, <0.1 mU/L):

• Proceed with radioiodine uptake scan after ultrasound to differentiate causes of thyrotoxicosis (Graves' disease, toxic adenoma, toxic multinodular goiter, or thyroiditis) 4.
• This functional imaging directly measures thyroid activity and guides treatment planning 4.
• Consider methimazole for symptom control in toxic multinodular goiter if surgery or radioactive iodine are not immediately appropriate 6.

If TSH is NORMAL (euthyroid):

• Ultrasound alone is sufficient for morphological evaluation 4.
• Do not proceed to radionuclide scanning, as it wastes resources and has low positive predictive value for malignancy in euthyroid patients 4, 1.
• Use ACR TI-RADS criteria from ultrasound to select nodules for fine-needle aspiration biopsy 1, 5.

If TSH is HIGH (hypothyroid):

• Imaging is generally not indicated, but if needed for goiter characterization, ultrasound is appropriate 4.

Step 4: Assess for Compressive Symptoms

• If the patient reports dyspnea, orthopnea, dysphagia, dysphonia, or choking sensation, obtain CT scan to evaluate for substernal extension and degree of tracheal compression 1, 3.
• CT is superior to ultrasound for evaluating substernal extension and retropharyngeal space involvement 1.
• These compressive symptoms indicate potential need for surgical intervention 2, 5.

Treatment Considerations

For Nontoxic Multinodular Goiter:

• Asymptomatic patients with benign cytology can be observed with yearly clinical follow-up 5, 7.
• Levothyroxine suppression therapy is controversial and should be avoided in patients with suppressed TSH to prevent iatrogenic hyperthyroidism 8, 7.
• Surgery is preferred for large goiters causing compressive symptoms 5, 8, 7.

For Toxic Multinodular Goiter:

• Treatment options include surgery or radioactive iodine therapy 6, 5, 7.
• Methimazole can ameliorate hyperthyroid symptoms in preparation for definitive therapy 6.

For Malignant or Suspicious Cytology:

• Refer for surgery immediately 1, 5.

Critical Pitfalls to Avoid

• Never attribute left arm discomfort to goiter without excluding cardiac disease first - this could be a fatal error.
• Do not skip TSH measurement before selecting imaging modality, as this leads to unnecessary testing and radiation exposure 4.
• Do not perform radionuclide scanning in euthyroid patients to determine malignancy or guide biopsy decisions 4, 1.
• Do not skip ultrasound and proceed directly to uptake scan, as this may miss coexisting thyroid nodules requiring malignancy evaluation 4.
• Do not use levothyroxine suppression in patients with already suppressed TSH, as this causes iatrogenic hyperthyroidism 8, 7.