A 40 years old women who has recently emigrated from Afghanistan to a practice to establish medical care . she complains only of mild fatigue and depression . Physical examination reveals a prominent , symmetrically enlarged thyroid about twice normal size . the remainder of the examination is normal . Questions : 1- What other features of the history should be elicited ? 2-What is the most likely cause of the patient's thyroid enlargment ? what is the pathogenetic mechanism of goiter formation in this disease ? 3- What laboratory tests should be ordered and why ?