A 75-year-old woman comes to the office with a 2-week history of palpitations, fatigue, heat intolerance, sweating, and weight loss. She was diagnosed with coronary artery disease 4 weeks ago after having chest pain. Coronary angiography revealed a high-grade stenosis in the right coronary artery; the patient was treated with angioplasty and stent placement and was discharged with prescriptions for aspirin, clopidogrel, atorvastatin, and metoprolol. She also has hypertension and type 2 diabetes mellitus, for which she takes hydrochlorothiazide, lisinopril, and metformin. The patient has a 20-pack-year smoking history but quit 10 years ago; she does not use alcohol or illicit drugs. Temperature is 37.2 C (99 F), blood pressure is 140/76 mm Hg, pulse is 120/min, and respirations are 18/min. Oxygen saturation by pulse oximetry is 96% on room air. On examination, the thyroid is slightly enlarged, firm, irregular, and nontender. There are no carotid bruits or jugular venous distension. The heart has a regular tachycardia with no murmurs or gallops. Bedside glucose is 130 mg/dL. ECG shows sinus tachycardia with no other significant abnormalities. The dose of the patient's beta blocker is increased, and she is sent for laboratory studies. Complete blood count, electrolytes, and hepatic transaminases are normal. Total T3 and free T4 are elevated, and TSH is undetectable. Thyrotropin receptor antibody assay is negative. Thyroid ultrasound reveals a multinodular goiter with increased vascularity. On follow-up 2 days later, the patient reports only partial relief of symptoms. Blood pressure is 135/80 mm Hg and pulse is 105/min. Which of the following is the best next step in management of this patient?

Question

A 75-year-old woman comes to the office with a 2-week history of palpitations, fatigue, heat intolerance, sweating, and weight loss.  She was diagnosed with coronary artery disease 4 weeks ago after having chest pain.  Coronary angiography revealed a high-grade stenosis in the right coronary artery; the patient was treated with angioplasty and stent placement and was discharged with prescriptions for aspirin, clopidogrel, atorvastatin, and metoprolol.  She also has hypertension and type 2 diabetes mellitus, for which she takes hydrochlorothiazide, lisinopril, and metformin.  The patient has a 20-pack-year smoking history but quit 10 years ago; she does not use alcohol or illicit drugs.  Temperature is 37.2 C (99 F), blood pressure is 140/76 mm Hg, pulse is 120/min, and respirations are 18/min.  Oxygen saturation by pulse oximetry is 96% on room air.  On examination, the thyroid is slightly enlarged, firm, irregular, and nontender.  There are no carotid bruits or jugular venous distension.  The heart has a regular tachycardia with no murmurs or gallops.  Bedside glucose is 130 mg/dL.  ECG shows sinus tachycardia with no other significant abnormalities.  The dose of the patient's beta blocker is increased, and she is sent for laboratory studies.  Complete blood count, electrolytes, and hepatic transaminases are normal.  Total T3 and free T4 are elevated, and TSH is undetectable.  Thyrotropin receptor antibody assay is negative.  Thyroid ultrasound reveals a multinodular goiter with increased vascularity.  On follow-up 2 days later, the patient reports only partial relief of symptoms.  Blood pressure is 135/80 mm Hg and pulse is 105/min.  Which of the following is the best next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_c139_2217_8f63_1b294ad03905_MD0005_00 This patient has symptomatic thyrotoxicosis following exposure to iodine-containing radiocontrast agents during coronary angiography, suggesting iodine-induced hyperthyroidism. Iodine-induced hyperthyroidism most often develops in patients with preexisting nodular thyroid disease, particularly in the setting of dietary iodine deficiency. These patients can develop areas of autonomously functioning thyroid tissue due to chronic TSH stimulation. Following an iodine load, excess iodine can serve as a substrate for increased thyroid hormone formation in the autonomous tissue (Jod-Basedow phenomenon). Common triggers include radiocontrast agents, amiodarone, topical antiseptics, and kelp-based dietary supplements. Iodine-induced thyrotoxicosis is usually self-limited if the source of iodine is discontinued. In mild cases, beta blockers may be sufficient for symptomatic management. However, antithyroid drugs such as thionamides (eg, methimazole) should be considered for persistent hyperthyroidism (>4-6 weeks), severe thyrotoxicosis, or older patients with underlying heart disease (such as this patient). (Choices C and E) Iodine-containing solutions (eg, Lugol solution) decrease release of thyroid hormone and inhibit thyroid hormone synthesis due to impaired organification of iodine in thyroid follicles (Wolff-Chaikoff phenomenon); they are used in prethyroidectomy management of patients with Graves disease and in acute management of thyroid storm. Radioactive iodine (RAI) ablation is useful in Graves disease and toxic nodular thyroid disease, in which increased iodine uptake concentrates the isotope in thyroid tissue. However, RAI ablation and iodine-containing solutions are unlikely to be effective in iodine-induced hyperthyroidism as the gland is already saturated with iodine. RAI ablation can also lead to permanent hypothyroidism, which would not be desirable in this patient with self-limited thyrotoxicosis. (Choice D) Prednisone is used for treatment of subacute (de Quervain) thyroiditis and destructive (type 2) amiodarone-induced thyroiditis, in which destruction of the gland leads to release of preformed thyroid hormone. It is also used to decrease conversion of T4 to T3 (active form) in patients with thyroid storm. However, thionamides are associated with fewer systemic side effects. Educational objective: Administration of iodine (eg, radiocontrast agents) to patients with chronic iodine deficiency or nodular thyroid disease can cause a transient hyperthyroid state. Symptomatic management with beta blockers is sufficient for most patients, but older patients with heart disease or those with persistent or severe hyperthyroidism should be treated with antithyroid drugs (eg, methimazole).

A 75-Year-Old Woman Comes to the Office with a 2-Week