A 66-year-old woman is admitted to the hospital with a 3-week history of worsening shortness of breath and palpitations. She has had severe dyspnea with minimal exertion. The patient has also experienced bilateral leg swelling and insomnia but no dizziness or chest pain. Medical history is notable for hypertension, type 2 diabetes mellitus, atrial fibrillation, heart failure, and hypercholesterolemia. Current medications are warfarin, amiodarone, metoprolol, metformin, atorvastatin, and lisinopril. Family history is unremarkable. The patient does not use tobacco, alcohol, or illicit drugs.
Blood pressure is 120/66 mm Hg and pulse is 120/min and irregular. On physical examination, there is mild lid lag but no proptosis. Visual field examination is normal. Neck examination shows elevated jugular venous pressure. The thyroid is irregular, enlarged, and nontender, and the left thyroid lobe is larger than the right. Crackles are heard in both lung bases. There is trace pedal edema and no pretibial myxedema.
Laboratory results are as follows:
Radioactive iodine uptake at 24 hours shows patchy uptake at 5% (normal: 10%-30%).
Which of the following is the most likely cause of the thyroid dysfunction in this patient?

Question

A 66-year-old woman is admitted to the hospital with a 3-week history of worsening shortness of breath and palpitations.  She has had severe dyspnea with minimal exertion.  The patient has also experienced bilateral leg swelling and insomnia but no dizziness or chest pain.  Medical history is notable for hypertension, type 2 diabetes mellitus, atrial fibrillation, heart failure, and hypercholesterolemia.  Current medications are warfarin, amiodarone, metoprolol, metformin, atorvastatin, and lisinopril.  Family history is unremarkable.  The patient does not use tobacco, alcohol, or illicit drugs.
Blood pressure is 120/66 mm Hg and pulse is 120/min and irregular.  On physical examination, there is mild lid lag but no proptosis.  Visual field examination is normal.  Neck examination shows elevated jugular venous pressure.  The thyroid is irregular, enlarged, and nontender, and the left thyroid lobe is larger than the right.  Crackles are heard in both lung bases.  There is trace pedal edema and no pretibial myxedema.
Laboratory results are as follows:
 Radioactive iodine uptake at 24 hours shows patchy uptake at 5% (normal: 10%-30%).
Which of the following is the most likely cause of the thyroid dysfunction in this patient?

Quizplus · Accepted Answer

11ec193a_96c7_6417_853d_eb2740588cfb_MD0002_00 This patient has overt thyrotoxicosis, with tachycardia, lid lag, elevated free T4 and T3 levels, and a suppressed TSH. In light of her decreased radioactive iodine uptake (RAIU), this is most likely due to amiodarone-induced thyrotoxicosis (AIT). Amiodarone can cause significant thyroid dysfunction due to its high iodine content, direct effects on thyroid follicular cells, and alteration of thyroid hormone metabolism. AIT can be caused by increased thyroid hormone synthesis (AIT type 1) or destruction of thyroid follicles with release of preformed hormone (AIT type 2), and patients may have features of both. Differentiating between these two subtypes is often difficult; RAIU is low but usually detectable in AIT type 1 and very low (<5%) or undetectable in AIT type 2. Doppler ultrasound shows hypervascularity in type 1 AIT but decreased vascularity in type 2. AIT type 1 is treated with methimazole to decrease new hormone synthesis, whereas AIT type 2 is treated with high-dose glucocorticoid therapy. (Choice B) Euthyroid sick syndrome refers to altered thyroid metabolism in patients with severe acute illness. Patients typically have low T3 levels (low T3 syndrome) due to decreased conversion of T4 to T3 but usually have normal T4 and TSH. This patient has elevated T3 and T4 and a suppressed TSH. (Choices C and E) Radioactive iodine uptake is normal to elevated in Graves disease (diffuse uptake) and toxic adenoma (focal uptake). This patient has decreased uptake. She also has no extrathyroidal features (eg, exophthalmos, pretibial myxedema, acropachy) of Graves disease. (Choice D) Subacute thyroiditis can present as thyrotoxicosis (elevated T3 and T4, suppressed TSH) with low RAIU. However, this condition usually follows a viral illness and is characterized by fever, neck pain, and a diffuse, tender goiter. Educational objective: Amiodarone can cause significant thyroid dysfunction due to its high iodine content, direct effects on thyroid follicular cells, and alteration of thyroid hormone metabolism. Amiodarone-induced thyrotoxicosis can be caused by increased thyroid hormone synthesis or destruction of thyroid follicles with release of preformed hormone. __________ References: Approach to the patient with amiodarone-induced thyrotoxicosis. (http://www.ncbi.nlm.nih.gov/pubmed/20525904)

A 66-Year-Old Woman Is Admitted to the Hospital with a 3-Week