Graves' disease

A 23- year- old woman presents with palpitations. Over the past 6 months, she has reported loose stools, a 10- lb ( 4.5- kg) weight loss despite a good appetite and food intake, and increased irritability. She appears to be anxious and has a pulse of 119 beats per minute and a blood pressure of 137/ 80 mm Hg. Her thyroid gland is diffusely and symmetrically enlarged to twice the normal size, and it is firm and non-tender; a thyroid bruit is audible. She has an eyelid lag, but no proptosis or periorbital edema. The serum thyrotropin level is 0.02 mu U per milliliter ( normal range, 0.35 to 4.50) and the level of free thyroxine is 4.10 ng per deciliter ( normal range, 0.89 to 1.76). How should she be further evaluated and treated?