Centre for Endocrinology, William Harvey Research Institute, Barts and London School of Medicine, Queen Mary University of London, London, UK.
Curr Opin Endocrinol Diabetes Obes. 2011 Aug;18(4):259-63. doi: 10.1097/MED.0b013e3283487193.
Cushing's syndrome results from prolonged and inappropriately high exposure of tissues to glucocorticoids. Biochemical tests are always needed to confirm the clinical suspicion: these include measurement of excess total endogenous cortisol secretion assessed by 24-h urinary free cortisol (UFC), loss of the normal feedback of the hypothalamo-pituitary-adrenal axis assessed by suppressibility after dexamethasone testing, and disturbance of the normal circadian rhythm of cortisol secretion assessed by midnight serum or salivary cortisol. This review focuses on recent data emerging on the value of UFC as a screening test for Cushing's syndrome.
Considerable evidence has emerged regarding the utility of UFC in the diagnosis of Cushing's syndrome because of its long-term use in clinical practice. Despite the fact that UFC assesses the active (free) component of cortisol, the methodological difficulties in 24-h urine collection and in assay precision have rendered this screening technique increasingly unpopular. Furthermore, the increased prevalence of mild, preclinical or cyclic Cushing's syndrome along with the fact that cortisol is not uniformly secreted during the day do not support its use as a screening test, although strikingly high levels can be useful.
Since the sensitivity and specificity of UFC are less than ideal when compared with other diagnostic modalities, we suggest the use of other more novel tests as first-step diagnostic tests to screen for hypercortisolaemia.
库欣综合征是由于组织长期、不适当的暴露于糖皮质激素所致。为了证实临床怀疑，总是需要进行生化检测：这些检测包括 24 小时尿游离皮质醇（UFC）评估的过量内源性总皮质醇分泌的测量、通过地塞米松试验评估的下丘脑-垂体-肾上腺轴正常反馈丧失、通过午夜血清或唾液皮质醇评估的正常皮质醇分泌昼夜节律紊乱。本综述重点关注 UFC 作为库欣综合征筛查试验的最新数据。
由于 UFC 在临床实践中的长期应用，大量证据表明其在库欣综合征的诊断中有一定的作用。尽管 UFC 评估了皮质醇的活性（游离）成分，但 24 小时尿液采集和检测精度的方法学困难使得这种筛查技术越来越不受欢迎。此外，轻度、临床前或周期性库欣综合征的患病率增加，以及皮质醇在一天中并非均匀分泌的事实，不支持将其作为筛查试验使用，尽管显著升高的水平可能是有用的。
与其他诊断方法相比，UFC 的敏感性和特异性都不理想，因此我们建议使用其他更新型的检测作为第一步诊断检测，以筛查高皮质醇血症。
