Examkin

Question

Difficulty: MediumMonitoring and Treatment Evaluation

A 72-year-old man comes to the clinic for a routine follow-up. He has a history of ischemic cardiomyopathy with a severely reduced left ventricular ejection fraction and recurrent, symptomatic ventricular tachycardia. He was started on amiodarone two years ago, which has successfully suppressed his arrhythmias. Over the past three months, the patient has developed progressive fatigue, increased sensitivity to cold, and a weight gain of 4.5 kg4.5\text{ kg} (9.9 lbs9.9\text{ lbs}). His other medications include lisinopril, metoprolol succinate, and aspirin. Vital signs show a blood pressure of 118/74 mmHg118/74\text{ mmHg} and a heart rate of 62/min62/\text{min}. Physical examination reveals delayed relaxation of the deep tendon reflexes.

Laboratory studies reveal:
Thyroid-stimulating hormone (TSH): 18.4 μU/mL18.4\text{ }\mu\text{U/mL} (Reference: 0.4−4.0 μU/mL0.4-4.0\text{ }\mu\text{U/mL})
Free T4: 0.5 ng/dL0.5\text{ ng/dL} (Reference: 0.9−1.7 ng/dL0.9-1.7\text{ ng/dL})

Which of the following is the most appropriate next step in the management of this patient?

  1. Continue amiodarone and begin levothyroxine therapyAnswer
  2. B
    Discontinue amiodarone and begin sotalol
  3. C
    Decrease the amiodarone dose by 50%50\% and repeat thyroid function tests in 66 weeks
  4. D
    Continue amiodarone and order a radioactive iodine uptake scan
  5. E
    Order an ultrasound of the thyroid gland

Answer

Continue amiodarone and begin levothyroxine therapy
The correct approach for amiodarone-induced hypothyroidism is to continue the amiodarone and administer exogenous levothyroxine. Amiodarone is highly efficacious for ventricular tachycardia, and its discontinuation in a patient with ischemic cardiomyopathy could result in fatal arrhythmias. Because amiodarone contains a large amount of iodine, it can induce hypothyroidism via the Wolff-Chaikoff effect (failure of the thyroid to escape the acute inhibitory effect of excess iodine on hormone synthesis). This side effect is easily and safely managed with levothyroxine supplementation.

Step-by-Step Solution

1
Analyze the patient's symptoms and laboratory results.
The patient exhibits fatigue, cold intolerance, weight gain, delayed reflexes, elevated TSH, and low free T4.
To establish the diagnosis of primary hypothyroidism.
2
Identify the underlying etiology of the hypothyroidism.
The hypothyroidism is an adverse effect of amiodarone, a medication with high iodine content that can inhibit thyroid hormone synthesis (Wolff-Chaikoff effect).
To determine if the etiology is related to the patient's pharmacological regimen.
3
Formulate a treatment plan that balances endocrine management with cardiovascular stability.
Initiate levothyroxine to treat the hypothyroidism while continuing amiodarone.
Amiodarone is effectively suppressing life-threatening ventricular tachycardia in a patient with ischemic cardiomyopathy. The endocrine side effect can be safely managed with exogenous hormone replacement without compromising arrhythmia control.

Key Concept

Patients who develop amiodarone-induced hypothyroidism should typically continue amiodarone (especially if it is controlling life-threatening arrhythmias) and be treated simultaneously with levothyroxine replacement therapy.
Estimated Time:1m 15s
Rate this question

Topics

Monitoring and Treatment Evaluation

More questions from this topic