What is the appropriate management for a patient with thyroid swelling, potentially caused by hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), with or without thyroid nodules?

Management of Thyroid Swelling

For a patient presenting with thyroid swelling, immediately measure serum TSH and perform thyroid ultrasonography to determine thyroid function status and characterize the structural abnormality—these two tests form the cornerstone of initial evaluation and guide all subsequent management decisions. 1, 2

Initial Diagnostic Approach

Essential First-Line Testing

• Measure serum TSH as the single most sensitive screening test for thyroid dysfunction, with sensitivity above 98% and specificity greater than 92% 3
• Perform thyroid ultrasonography to evaluate thyroid morphology, identify nodules, assess for suspicious features of malignancy, and provide thyroid dimensions 1, 4
• If TSH is abnormal, measure free T4 to distinguish between subclinical (normal free T4) and overt (abnormal free T4) thyroid dysfunction 3

Interpreting TSH Results to Guide Management

The TSH level determines the clinical pathway:

• TSH >4.5 mIU/L (Hypothyroidism): Indicates underactive thyroid requiring levothyroxine therapy, particularly if TSH >10 mIU/L or if symptomatic 3
• TSH 0.45-4.5 mIU/L (Normal): Focus shifts entirely to structural evaluation via ultrasound to assess nodules and exclude malignancy 1, 3
• TSH <0.45 mIU/L (Hyperthyroidism): Indicates overactive thyroid requiring radionuclide uptake scan to determine etiology (Graves disease, toxic nodular goiter, or thyroiditis) 1, 5

Management Based on Thyroid Function Status

Hypothyroidism with Thyroid Swelling (Elevated TSH)

Initiate levothyroxine therapy immediately for patients with TSH >10 mIU/L or symptomatic patients with any degree of TSH elevation, as untreated hypothyroidism causes cardiovascular dysfunction, adverse lipid profiles, and decreased quality of life. 3

Levothyroxine Dosing Strategy

• For patients <70 years without cardiac disease: Start at full replacement dose of approximately 1.6 mcg/kg/day 3
• For patients >70 years or with cardiac disease: Start at 25-50 mcg/day and titrate gradually to avoid precipitating cardiac ischemia or arrhythmias 3
• Monitor TSH every 6-8 weeks during dose titration, adjusting by 12.5-25 mcg increments until TSH normalizes to 0.5-4.5 mIU/L 3

Critical Safety Consideration

• Before initiating levothyroxine, rule out concurrent adrenal insufficiency, especially in suspected central hypothyroidism, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis 3

Hyperthyroidism with Thyroid Swelling (Suppressed TSH)

Initiate β-blocker therapy immediately (propranolol, atenolol, or metoprolol) to control cardiac symptoms while determining the underlying cause with radionuclide uptake scan. 5, 6

Determining Etiology with Radionuclide Scan

• Increased uptake: Graves disease or toxic nodular goiter—treat with radioactive iodine (preferred in US), antithyroid drugs (methimazole), or surgery 1, 6
• Decreased uptake: Thyroiditis—provide symptomatic treatment only, as hyperthyroidism is transient and self-limited 1, 5

Treatment Algorithm for Confirmed Hyperthyroidism

• Radioactive iodine is the treatment of choice in the United States for Graves disease, toxic multinodular goiter, and toxic adenoma in patients without contraindications 6
• Antithyroid drugs (methimazole) are alternatives, particularly in pregnancy or when radioactive iodine is contraindicated 6
• Thyroidectomy is reserved for cases where other treatments fail, are contraindicated, or when goiter causes compressive symptoms 6

Euthyroid Thyroid Swelling (Normal TSH)

When TSH is normal, the swelling represents either diffuse goiter or nodular thyroid disease without functional abnormality. Management focuses entirely on structural assessment and malignancy risk stratification via ultrasound. 1, 7

Ultrasound-Guided Management of Thyroid Nodules

• Nodules with suspicious ultrasound features (microcalcifications, irregular margins, taller-than-wide shape, hypoechogenicity) require fine-needle aspiration biopsy (FNA) under ultrasound guidance 7, 4
• Nodules >1 cm with intermediate suspicion features warrant FNA to exclude malignancy 7, 4
• Nodules <1 cm without suspicious features can be followed with serial ultrasound at 6-12 month intervals 4, 8
• Multiple nodules (multinodular goiter): Compare ultrasound to radionuclide scan to identify hypofunctioning or isofunctioning nodules requiring targeted biopsy 1

When to Consider Surgery for Benign Goiter

• Compressive symptoms (dysphagia, dyspnea, hoarseness) that impair quality of life 1, 6
• Substernal extension causing tracheal deviation or compression 1
• Cosmetic concerns significantly affecting patient well-being 1

Special Considerations and Common Pitfalls

Critical Pitfalls to Avoid

• Never assume thyroid swelling is benign without TSH measurement and ultrasound evaluation—7-15% of thyroid nodules harbor malignancy 4
• Do not perform imaging for hypothyroidism workup in adults—imaging does not differentiate causes of hypothyroidism, and all causes show decreased radioiodine uptake 1
• Avoid treating based on single elevated TSH value—30-60% of elevated TSH levels normalize spontaneously on repeat testing after 3-6 weeks 3
• Never start levothyroxine before ruling out adrenal insufficiency in suspected central hypothyroidism, as this precipitates adrenal crisis 3

Monitoring After Treatment Initiation

• For hypothyroidism: Recheck TSH and free T4 every 6-8 weeks during dose titration, then annually once stable 3
• For hyperthyroidism: Monitor thyroid function every 4-6 weeks initially, then every 3-6 months after achieving euthyroid state 5, 6
• For nodules under surveillance: Repeat ultrasound at 6-12 months initially, then annually for benign nodules 1, 4

Pregnancy Considerations

• Women planning pregnancy with elevated TSH require immediate treatment before conception, targeting TSH <2.5 mIU/L, as untreated hypothyroidism increases risk of preeclampsia, low birth weight, and neurodevelopmental deficits 3
• Pregnant women with hyperthyroidism require antithyroid drugs (propylthiouracil in first trimester, methimazole thereafter) rather than radioactive iodine, which is absolutely contraindicated 6