A 24-year-old man comes to the physician for a 1-week history of neck pain and palpitations. He has had a 5-lb weight loss during this time. His pulse is 110. Examination shows an enlarged thyroid gland. A 2/6 systolic ejection murmur is heard along the left sternal border. Serum T4 is elevated. A radioiodine uptake scan shows decreased uptake. Which of the following is the most likely diagnosis?
Adenoma
Lymphocytic infiltration and anti-microsomal antibodies
Release of pre-formed thyroid hormone
Surreptitious thyrotoxicosis
Thyroid-stimulating immunoglobulin
