WBR1027

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	USMLE Step 3
Main Category	Primary Care Office
Sub Category	Cardiovascular
Prompt	A 60 year-old female comes to your office complaining of unexplained weight loss, sweating, and tremor. These symptoms started gradually over the last month. The patient has a past medical history of hypertension for 15 years which is controlled by Metoprolol and hydrochlorothiazide, thyroiditis which was treated successfully with corticosteroids 3 years ago, and atrial fibrillation 1 year ago which is controlled by amiodarone and warfarin with controlled INR. On examination, the patient is vitally normal except of recent tachycardia with rate of 100 beat per minute. There is no pain or swelling in her neck. There is marked increase in serum levels of free T4, with undetectable levels of serum TSH. What is the most probable cause of these symptoms?
Answer A	Metoprolol
Answer A Explanation	Incorrect Amiodarone-induced thyrotoxicosis (AIT) is the cause in this patient.
Answer B	Warfarin
Answer B Explanation	Incorrect Amiodarone-induced thyrotoxicosis (AIT) is the cause in this patient.
Answer C	Inflammatory
Answer C Explanation	Incorrect Amiodarone-induced thyrotoxicosis (AIT) is the cause in this patient.
Answer D	Anti arrhythmic medication
Answer D Explanation	Correct Amiodarone-induced thyrotoxicosis (AIT) is the cause in this patient.
Answer E	hydrochlorothiazid
Answer E Explanation	Incorrect Amiodarone-induced thyrotoxicosis (AIT) is the cause in this patient.
Right Answer	D
Explanation	Amiodarone-induced thyrotoxicosis (AIT) occurs in 2–12% of patients on chronic amiodarone treatment. In patients with pre-existing thyroid abnormalities, thyrotoxicosis is believed to result from: Type I AIT is believed to result from iodine-induced excessive thyroid hormone synthesis. Type II AIT results from glandular damage with consequent release of preformed thyroid hormones into the circulation. It is usually self-limiting, which may be explained by the dose-dependent cytotoxic effect of amiodarone. Reference: "Effects of amiodarone on thyroid function.",journal = Ann Intern Med, volume = 126, issue = 1, month = Jan, year = 1997, PMID = 8992925. "Amiodarone and the thyroid: a practical guide to the management of thyroid dysfunction induced by amiodarone therapy.", journal = Heart, volume = 79, issue = 2, month = Feb, year = 1998, PMID = 9538302. Educational Objective: References:
Approved	No
Keyword	[[WBRKeyword::Amiodarone]]
Linked Question
Order in Linked Questions