Circadian Rhythm of salivary cortisol in healthy normal weight and obese children and adolescents

BALLERINI MG; RODRIGUEZ ME; AMARO A; RUBINO C; BERGADÁ I; ROPELATO M

Purto Varas

Congreso; XXV Annual Meeting SLEP; 2015

Sociedad Latinoamericana de Endocrinología Pediátrica

Background: Previous studies showed divergences regarding the impact of obesity on circadian rhythm (CR) of salivary cortisol (SAF) in children. Reference values of CR SAF are still lacking using ultrasensitive electrochemiluminescent immunoassay (ECLIA).Objective: To test the influence of BMI, age, gender, attending school or during summer-break on CR of SAF in children. Methods:Prospective-descriptive-cohort study. Saliva was collected by spitting into tubes at 8:00 AM (mSAF) and 11:00 PM (nSAF). Collection procedure was evaluated by a questionnaire. SAF was measured by ECLIA (Cobase411-Roche) in 103 healthy children (53 girls; 1.8?18 yr (median: 10 yr). Inclusion criteria: healthy children without acute or known chronic diseases at the time of the study. Exclusion criteria: corticosteroid therapy, incomplete sampling/erroneous time collection. Interindividual SAF variation (bCV%) and the decrease percentage of cortisol at night (D%) = [(mSAF-nSAF)/mSAF]x100 were calculated. Children were divided according to BMI-centile into Lean (L, n = 59), overweight (Ow, n = 12) or obese (Ob, n = 32). Obese children had no clinical signs of hypercortisolism.Results: Eighty-four percentage of children referred no difficulties in salivary collection. SAF widely varied in children (bCV% mSAF: 50% and nSAF: 42%) while D% variation was 27%. Multiple regression showed that SAF (nmol/L) was not associated to BMI [Median mSAF; (3rd-97thcentile range) in L: 16; (3?35), Ow: 10; (8?20), Ob: 14; (4?47), p = 0.07; nSAF in L: 4; (1.4?8), Ow: 4; (2?7), Ob: 5; (1.2?9), p = 0.52]. Median mSAF concentration for the whole group of children was 14 nmol/L, 3rd-97thcentile range: 5?34 nmol/L. Age and attending school period were significantly associated to higher nSAF (r = 0.41, p < 0.01) and a lesser %D (r = ?0.32, p < 0.001). Children older than 10 years of age had significantly higher nSAF compared to younger children (97thcentile: 8.0 vs 6.5 nmol/L, p = 0.001), whereas the proportion of children during summer-break was comparable between these two age groups (p = 0.97). Conclusion: Obesity seems not to influence CR SAF in normal children and adolescents. Age should be taken into account when evaluating nocturnal free cortisol in saliva. Manufactures do not provide morning or night SAF references for pediatric settings, hence, our cut-off values could be useful in children in whom abnormal secretion of cortisol is suspected.