A 69‑year‑old woman with hypertension and atrial fibrillation on amiodarone, metoprolol succinate, amlodipine, and apixaban presents with fatigue, cold intolerance, dry skin, weight gain, delayed reflexes, and labs showing elevated TSH and low free T4 consistent with primary hypothyroidism. What is the most appropriate next step: discontinue amiodarone, discontinue amlodipine, obtain thyroid ultrasound, start levothyroxine, or refer to endocrinology?

Prescribe Levothyroxine Immediately

This patient has overt primary hypothyroidism (TSH 6.2 mIU/L with low free T4 0.6) presenting with classic symptoms—fatigue, cold intolerance, dry skin, weight gain, and delayed reflexes—and the most appropriate next step is to prescribe levothyroxine. 1

Why Levothyroxine is the Correct Answer

Diagnostic Confirmation

• The combination of elevated TSH (6.2 mIU/L, above the reference range of 0.45-4.5 mIU/L) with low free T4 (0.6) definitively establishes overt primary hypothyroidism, not subclinical disease 1, 2
• Her clinical presentation—fatigue, cold intolerance, dry skin, unintentional weight gain, delayed reflexes—represents classic hypothyroid symptoms that occur in 68-83% (fatigue), 24-59% (weight gain) of hypothyroid patients 2, 3, 4
• Overt hypothyroidism requires immediate treatment to prevent cardiovascular dysfunction, adverse lipid profiles, and quality of life deterioration 1, 2

Amiodarone's Role (But Not a Reason to Discontinue)

• Amiodarone causes hypothyroidism in 2-10% of patients by inhibiting peripheral conversion of T4 to T3 and releasing large amounts of inorganic iodine 5, 6
• Amiodarone-induced hypothyroidism (AIH) develops more commonly in iodine-sufficient areas and responds favorably to thyroid hormone replacement therapy 6
• Critically, stopping amiodarone has little short-term benefit because it is lipophilic with a long half-life, and thyroid dysfunction can persist for weeks to months after discontinuation 5, 6
• The patient's atrial fibrillation requires continued amiodarone therapy, and discontinuing it would risk arrhythmia breakthrough without resolving her hypothyroidism 5

Why Other Options Are Incorrect

Discontinue Amiodarone (Wrong)

• While amiodarone likely caused her hypothyroidism, stopping it will not provide short-term relief due to its prolonged half-life 5, 6
• Her atrial fibrillation requires antiarrhythmic therapy, and discontinuing amiodarone risks arrhythmia recurrence 5
• The correct approach is to continue amiodarone while treating hypothyroidism with levothyroxine 6

Discontinue Amlodipine (Wrong)

• Amlodipine does not cause hypothyroidism and has no role in thyroid dysfunction 1
• Her blood pressure is already 100/60 mmHg, and discontinuing amlodipine could worsen hypertension control 1

Order Thyroid Ultrasound (Wrong)

• The American College of Radiology explicitly states there is no role for imaging in the workup of hypothyroidism in adults 7
• Imaging cannot differentiate among causes of hypothyroidism, and all causes show decreased radioiodine uptake regardless of gland appearance 7
• The diagnosis is established by laboratory testing (elevated TSH with low free T4), not imaging 7, 1

Refer to Endocrinologist (Wrong)

• Primary hypothyroidism is straightforward to diagnose and treat in primary care 1, 2
• Endocrinology referral is unnecessary for uncomplicated overt hypothyroidism 1
• Referral would delay treatment and is not indicated when the diagnosis is clear 1

Levothyroxine Dosing Strategy

Initial Dose Considerations

• For patients >70 years or with cardiac disease (this patient has atrial fibrillation and coronary blockages), start with 25-50 mcg daily to avoid precipitating cardiac ischemia or arrhythmias 1, 2
• Her age (69), atrial fibrillation, and recent cardiac evaluation showing "multiple blockages" mandate a conservative starting dose 1, 2
• Increase by 12.5-25 mcg every 6-8 weeks based on TSH response until target TSH of 0.5-4.5 mIU/L is achieved 1

Critical Safety Precaution

• Before initiating levothyroxine, obtain morning cortisol and ACTH to exclude adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis 1
• This is especially important in patients with autoimmune thyroid disease (likely Hashimoto's given the clinical context) 1

Monitoring Protocol

• Recheck TSH and free T4 in 6-8 weeks after starting levothyroxine, as this represents the time needed to reach steady state 1
• Once TSH normalizes, monitor every 6-12 months or sooner if symptoms change 1
• Target TSH of 0.5-4.5 mIU/L with normal free T4 1, 2

Common Pitfalls to Avoid

Do Not Delay Treatment

• Untreated hypothyroidism causes cardiac dysfunction (delayed relaxation, abnormal cardiac output), adverse lipid profiles, and can progress to myxedema coma with 30% mortality 1, 2
• Her existing cardiac disease makes prompt treatment even more critical 2

Do Not Overtitrate

• Approximately 25% of patients on levothyroxine are unintentionally overtreated with suppressed TSH, increasing risks of atrial fibrillation (3-5 fold), osteoporosis, fractures, and cardiovascular mortality 1
• Given her atrial fibrillation, avoiding TSH suppression below 0.45 mIU/L is particularly important 1

Do Not Stop Amiodarone Prematurely

• Amiodarone's effects on thyroid function persist for weeks to months after discontinuation due to its long half-life 5, 6
• Continue amiodarone for arrhythmia control while treating hypothyroidism with levothyroxine 6

Do Not Order Unnecessary Imaging

• Thyroid ultrasound provides no diagnostic value for hypothyroidism and should not be performed 7
• Imaging is only indicated if a palpable thyroid nodule is detected on physical examination 7

Expected Clinical Outcomes

• Levothyroxine will stabilize weight and improve energy within 6-8 weeks of adequate replacement 1
• Dry skin, cold intolerance, and delayed reflexes should resolve with normalization of thyroid hormone levels 2, 3, 4
• Treatment may improve her cardiac function and lower LDL cholesterol 1, 2
• Most patients with hypothyroidism can lead normal, healthy lives with appropriate levothyroxine therapy 8, 2