title: Late-night salivary cortisol as a screening test for the diagnosis of Cushing's syndrome in Japan.
abstract: Measurement of late-night and/or midnight salivary cortisol currently used in US and European countries is a simple and convenient screening test for the initial diagnosis of Cushing's syndrome (CS). Unfortunately, this test has not been widely used in Japan. The purpose of this study was to evaluate the usefulness of the measurement of late-night salivary cortisol as a screening test for the diagnosis of CS in Japan. We studied 27 patients with various causes of CS, consisting of ACTH-dependent Cushing's disease [5] and ectopic ACTH syndrome [4] and ACTH-independent adrenal CS [11] and subclinical CS [7]. Eleven patients with type 2 diabetes and obesity and 16 normal subjects served as control group. Saliva samples were collected at late-night (23:00) in a commercially available device and assayed for cortisol by radioimmunoassay. There were highly significant correlations (P<0.0001) between late-night serum and salivary cortisol levels in normal subjects (r = 0.861) and in patients with CS (r = 0.788). Late-night salivary cortisol levels in CS patients (0.975 +/- 1.56 microg/dl) were significantly higher than those in normal subjects (0.124 +/- 0.031 microg/dl) and in obese diabetic patients (0.146 +/- 0.043 microg/dl), respectively. Twenty-five out of 27 CS patients had late-night salivary cortisol concentrations greater than 0.21 microg/dl, whereas those in control group were less than 0.2 microg/dl. Receiver operating characteristic curve (ROC) analysis showed that the cut-off point of 0.21 microg/dl provides a sensitivity of 93% and a specificity of 100%. Therefore, it is concluded that the measurement of late-night salivary cortisol is an easy and reliable noninvasive screening test for the initial diagnosis of CS, especially useful for large high-risk populations, such as diabetes and obesity.
authors.affiliation: Department of Clinical and Molecular Endocrinology, Tokyo Medical and Dental University Graduate School, Japan.
authors.forename: Masaru
authors.initials: M
authors.lastname: Doi
authors.forename: Naoko
authors.initials: N
authors.lastname: Sekizawa
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tani
authors.forename: Kyoichiro
authors.initials: K
authors.lastname: Tsuchiya
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kouyama
authors.forename: Toru
authors.initials: T
authors.lastname: Tateno
authors.forename: Hajime
authors.initials: H
authors.lastname: Izumiyama
authors.forename: Takanobu
authors.initials: T
authors.lastname: Yoshimoto
authors.forename: Yukio
authors.initials: Y
authors.lastname: Hirata
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002940:Circadian Rhythm; D003480:Cushing Syndrome / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis* / Q000097:blood / Q000652:urine; D007564:Japan; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D012463:Saliva / Q000737:chemistry*
chemical_list: D006854:Hydrocortisone