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

Puerto Varas

Congreso; XXV Congreso de la Sociedad Latinoamericana de Endocrinología Pediátrica; 2015

Sociedad Latinoamericana de Endocrinologia Pediátrica (SLEP)

Background: Previous studies showed divergences regarding the impact of obesity on salivary cortisol (SAF) circadian rhythm (CR) in children. Reference values of SAF CR are still lacking using ultrasensitive electrochemiluminescent immunoassay (ECLIA).Objective: To test the influence of BMI and age, gender, body surface (BS) and school summer-break on circadian rhythm of SAF in children. Methods: Prospective-descriptive-cohort study. Saliva was collected by spitting into plastic tubes at 8:00AM (mSAF) and 11:00PM (nSAF). The 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 infectious disease or known chronic disease at the time of the study, written consent. 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 sign of hypercortisolism. Results: 84% 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]. Age, BS and school period in children were positively associated to nSAF concentration (r= 0.41, p