2. 25歲女性因心悸、體重2個月減輕3公斤來診,身體檢查pulse rate100/min,regular,頸部摸不到甲狀腺,抽血檢查free T4 > 4.0 ng/dl、hsTSH < 0.004 μU/ml,thyroglobulin 3 ng/ml,I-131 uptake 2hr 2%、24hr 5%,antimicrosomal antibody(-),下列哪一診斷最有可能
(A) Hashimoto's thyroiditis
(B) Subacute thyroditis
(C) Graves' disease
(D) Thyroid cancer
(E) Exogenous thyroxine