Department of Endocrinology and Metabolism, Hirosaki University Graduate School of Medicine, Aomori, Japan.
Endocr J. 2010;57(4):331-7. doi: 10.1507/endocrj.k09e-340. Epub 2010 Feb 7.
As a screening test for Cushing's syndrome, the evaluation of late-night cortisol levels is indispensable. We evaluated the usefulness and accuracy of plasma, urinary, and salivary cortisol levels measured late at night for the diagnosis of Cushing's syndrome. High cortisol levels (> 5 microg/dL) during the night are indicative of Cushing's syndrome, although night plasma cortisol levels are not readily reproducible because of the stressful situation. There was no correlation between plasma and urinary cortisol levels late at night, and late-night urinary cortisol levels provided weak information for the diagnosis of Cushing's syndrome. By contrast, late-night plasma and salivary cortisol levels showed a positive correlation, and salivary cortisol sampling was found to be useful for the diagnosis of Cushing's syndrome, because more than 0.4 microg/dL of late-night salivary cortisol levels gave a sensitivity of 86% and a specificity of 100% in our hospital. This method is also useful for the diagnosis of early or mild stage Cushing's syndrome, so-called subclinical Cushing's syndrome. Inherent differences between assays make it difficult to define optimal diagnostic criteria. However, the relative levels of salivary cortisol ratio, which is presented as a relative level, compared with the mean levels of healthy subjects in each institute, is useful for the screening of Cushing's syndrome as the cut-off level of 1.5 shows both high sensitivity and specificity in subclinical and overt Cushing's syndrome. Late-night salivary cortisol measurement is therefore a primary method of choice in the screening of patients suspected of having Cushing's syndrome.
作为库欣综合征的筛查试验，评估深夜皮质醇水平是必不可少的。我们评估了深夜测量的血浆、尿液和唾液皮质醇水平对库欣综合征诊断的有用性和准确性。夜间皮质醇水平升高（>5μg/dL）提示库欣综合征，但由于应激状态，夜间血浆皮质醇水平不易重现。夜间血浆和尿液皮质醇水平之间没有相关性，夜间尿液皮质醇水平对库欣综合征的诊断提供的信息很弱。相比之下，深夜血浆和唾液皮质醇水平呈正相关，唾液皮质醇采样对库欣综合征的诊断很有用，因为在我们医院，超过 0.4μg/dL 的深夜唾液皮质醇水平的灵敏度为 86%，特异性为 100%。这种方法也可用于诊断早期或轻度库欣综合征，即所谓的亚临床库欣综合征。由于测定方法之间存在固有差异，因此很难定义最佳诊断标准。然而，与每个研究所的健康受试者的平均水平相比，唾液皮质醇比值的相对水平（表示为相对水平）对于库欣综合征的筛查很有用，因为 1.5 的截断值在亚临床和显性库欣综合征中均显示出高灵敏度和特异性。因此，深夜唾液皮质醇测量是疑似库欣综合征患者筛查的首选方法。
