Hyperthyroidism can be caused by all of the following except:

E. Medullary carcinoma of the thyroid.

DISCUSSION: Common types of hyperthyroidism include diffuse toxic goiter (Graves' disease, named after the Dublin physician Robert Graves who described it in 1835 but known since its original description by Parry in 1786 and described by von Basedow in 1840) and toxic adenoma or toxic multinodular goiter (Plummer's disease). Uncommon causes include thyrotoxicosis factitia, functioning metastatic thyroid carcinoma, trophoblastic tumors that secrete human chorionic gonadotropin (having thyroid-stimulating properties), inappropriate secretion of thyrotropin by pituitary tumors, struma ovarii, iodide-induced hyperfunction, and thyroiditis.