6. 60歲男性因耳鳴做了頭部核磁共振,發現腦下垂體有一5mm腺瘤而來診,除了耳鳴外病人並無其他不適,外觀亦無內分泌疾病外觀。抽血檢查 Cortisol 8 AM 15ug/dl,plasma ACTH 20 pg/ml, FSH 4 IU/L, LH 5 IU/L,free T4 1.1 ng/dl,Testosterone 427 ng/dl, IGF-1 165 ng/ml,TSH 1.0 uU/ml。下列處置何者最恰當?
(A) Transsphenoidal surgery
(B) gamma-knife radiotherapy
(C) No treatment
(D) Octreotide therapy
(E) Dostinex therapy