A 41-Year-Old Man Comes to the Office for Routine Follow

A 41-year-old man comes to the office for routine follow up. He feels fatigue, headache, weight loss, sweating, and palpitations. He is otherwise healthy and takes no medications. He does not use tobacco, alcohol, or illicit drugs. Physical examination reveals lid lag and a fine hand tremor. Neck examination reveals mild, diffuse enlargement of the thyroid gland. Laboratory results are high TSH and T4, T3: Which of the following is the most likely cause of this patient's disorder?

A) Elevated thyroxine-binding globulin
B) Graves disease
C) Painless thyroiditis
D) Pituitary tumor
E) Thyroid cancer