Clin Chem Lab Med 2017; aop Sabrina Coelli, Camila Bergonsi Farias, Ariana Aguiar Soares, Gabriele Martins Crescente, Vânia Naomi Hirakata, Luiza Barboza Souza, Mauro Antônio Czepielewski, Joíza Lins Camargo and Sandra Pinho Silveiro* Influence of age, gender and body mass index on late-night salivary cortisol in healthy adults DOI 10.1515/cclm-2016-1100 Received December 4, 2016; accepted March 28, 2017 Abstract Background: Late-night salivary cortisol (LNSC) is one of the most reliable tests to screen for endogenous Cushing syndrome. This test is simple, inexpensive and noninva- sive and has high sensitivity and specificity. The aim of our study was to analyze the putative influence of age, gender and body mass index (BMI) on LNSC levels in a healthy population. Methods: Cross-sectional study conducted in healthy adults. Midnight saliva samples were collected at home. Participants refrained from teeth brushing, eating or drinking for 2 h prior to collection. Salivary cortisol measured by electrochemiluminescence immunoassay (ECLIA). The study was approved by the Ethics Committee of the hospital (number 140073). Results: We evaluated 122 nonsmoking healthy volun- teers. Mean age was 35 ± 14 years (range, 18–74 years); 63% were women. Mean BMI was 24 ± 3 kg/m 2 , blood pressure 115/74 mmHg and fasting plasma glucose 4.8 ± 0.5 mmol/L. LNSC presented a non-Gaussian distribution; the median was 3.58 (range, 0.55–8.55) nmol/L (0.13 [range, 0.02–0.31] μg/dL), and the 97.5th percentile (P97.5) was 8.3 nmol/L (0.3 μg/dL). Multiple linear regression disclosed a sig- nificant positive association between salivary cortisol levels and age (r 2 = 0.21, p < 0.001), but no association with gender (p = 0.105) or BMI (p = 0.119). Accordingly, partici- pants aged >50 years had significantly higher salivary cortisol as compared to those aged <50 years (5.24 nmol/L [0.19 μg/dL] vs. 3.31 nmol/L [0.12 μg/dL], respectively, p < 0.001). Conclusions: The maximum reference value (P97.5) of LNSC was set at 8.3 nmol/L (0.3 μg/dL) using ECLIA. Advanced age was associated with higher LNSC levels, with no evident influence of gender or BMI. Keywords: age; body mass index; Cushing; cutoff; gender; late-night salivary cortisol. Introduction Endogenous Cushing’s syndrome is a disorder resulting from prolonged and excessive exposure to cortisol, which can be ACTH dependent (i.e. of pituitary or ectopic origin) or independent (cortisol overproduction by benign or malignant adrenal lesions) [1]. This syndrome is charac- terized by the presence of central obesity, facial round- ness, purple striae, proximal myopathy, hypertension, osteoporosis and diabetes, among other characteristics [1, 2]. Important concerns include cardiovascular complica- tions (myocardial infarction and cardiac failure) and psy- chiatric sequelae, as well as massive immunosuppression, with development of serious and often fatal infections [2, 3]. Therefore, early and accurate diagnosis is of the utmost importance. According to current guidelines, the tests recom- mended for initial screening of Cushing’s syndrome are late-night salivary cortisol (LNSC), 24-h urine-free cortisol, and the 1-mg overnight dexamethasone suppression test. Elevated cortisol levels on these tests suggest diagnosis of the syndrome [2, 4]. Measurement of salivary cortisol is unequivocally one of the central exams. It is an accurate *Corresponding author: Sandra Pinho Silveiro, Serviço de Endocrinologia, HCPA, Rua Ramiro Barcelos, 2350 – Prédio 12, 4° andar, Porto Alegre, RS, Brazil, Phone: +55.51.33598127, Fax: +55.51.33599255, E-mail: ssilveiro@hcpa.edu.br; Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; and Endocrinology Unit, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil Sabrina Coelli, Camila Bergonsi Farias, Ariana Aguiar Soares and Luiza Barboza Souza: Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil Gabriele Martins Crescente and Vânia Naomi Hirakata: Endocrinology Unit, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil Mauro Antônio Czepielewski and Joíza Lins Camargo: Graduate Program in Medical Sciences: Endocrinology, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; and Endocrinology Unit, Hospital de Clínicas de Porto Alegre (HCPA), Porto Alegre, RS, Brazil Brought to you by | Univ-bibl. Carolinenbiblioteket Authenticated Download Date | 5/23/17 2:40 PM