Hypothyroidism Quiz: Ace Your Exams

A 52-year-old woman comes to the PA complaining of decreased libido for the past 4 weeks. Over the last month, she has also gained 3.2 kg (7 lb) despite no increase in appetite or food intake. She has a history of Graves disease treated with radioactive iodine 3 years ago, and she is now on daily levothyroxine. Two months ago, the patient started taking iodine tablets daily because she read it “helps reduce wrinkles.” The patient’s temperature is 37.0°C (98.6°F), pulse is 56/min, and blood pressure is 124/88 mm Hg. Physical examination shows cold, dry skin. Heart and lung sounds are normal. Neck palpation reveals no tenderness or masses. Capillary refill is less than 2 seconds. There is delayed tendon reflex relaxation in the lower extremities. Laboratory testing is obtained and reveals the following:  



Which of the following is the most likely etiology of this patient’s clinical presentation?