庫欣氏症候群實驗室診斷之介紹

An Introduction to the Laboratory Diagnosis of Cushing's Syndrome

庫欣氏症候群依病因分為ACTH-dependent，包括垂腺性及異位性；及ACTH-indendent，即腎上腺性。實驗室診斷皆為三步驟－（一）篩檢或確定步驟，利用單劑量迪皮醇抑制試驗及UFC來篩檢懷疑患者，並進一步利用LDDST及LDDST/CRHT test來確定哪些患者為庫欣氏症候群。（二）鑑別診斷步驟，利用血漿ACTH測定，來區分庫欣氏症候群患者為ACTH-dependent及ACTH-dependent患者，區分為垂腺或異位性。（三）腫瘤定位，若患者為腎上腺性，應施行腎上腺CT scan；若為垂腺性，應施行蝶鞍MRI，當MRI無法確定腫瘤時，可施行BIPSS，進一步定位腫瘤所在；若為異位性，應施行肺部、縱膈腔侑腹部之CT scan，必要時可施行octreotide核子醫學掃瞄。

Cushing's syndrome, a status of chronic, sustained hypersecretion of cortisol, can be divided into ACTH-dependent, in which the excessive ACTH secretion comes from a pituitary tumor (Cushing's disease) or a neuroendocrine tumor (ectopic), and ACTH-independent, in which the excessive production of corisol comes from adrenal tumors. The first step of laboratory diagnosis is to screen suspected patients using the single dose dexamethasone suppression test and urine free cortisol determination, and then to confirm further hypersecretion of cortisol by LDDST and LDDST/CRH test. The second step of laboratory diagnosis is to differentiate proven patients with Cushing's syndrome into ACTH-dependent and independent by plasma ACTH-IRMA, and then to distinguish further Cushing's disease patients from those with ectopic ACTH syndrome using the HDDST, CRH test and desmopressin test. In the third step of tumor localization, adrenal CT scan is sufficient for adrenal Cushing's syndrome; MRI of sella is better than CT scan for the localization of pituitary microadenoma causing Cushing's diease. If MRI of sella is negative, BIPSS is indicated. For patients with ectopic Cushing's syndrome, CT scan of lung, mediastium and abdomen should be performed. If bronchial carcinoid is suspected, octreotide radionuclectide scanning is helpful.