Diurnal salivary cortisol concentration in school-aged children: increased morning cortisol concentration and total cortisol concentration negatively correlated to body mass index in children with recurrent abdominal pain of psychosomatic origin.

INTRODUCTION: The sampling method for salivary cortisol is sensitive, specific and pain-free. Our knowledge about cortisol concentration in saliva and plasma in school-aged children is sparse and contradictory. AIM: To estimate diurnal variation in salivary cortisol concentration in children with and without psychosomatic recurrent abdominal pain (RAP), and to compare groups and relate the concentrations to age, sex, puberty, body mass index (BMI), allergy, headache and ethnicity. CHILDREN AND METHOD: Saliva was collected in 'Salivette' tubes from 159 healthy girls and 147 healthy boys, aged 5-15 years, and from 25 girls and 6 boys, aged 6-18 years, with RAP of psychosomatic origin, at 08.00 h, 13.00 h and 20.00 h. Saliva was analysed using a commercial RIA-cortisol kit. RESULTS: The median concentrations in healthy girls and boys were 8.8/8.3 nmol/l at 08.00 h, 5.5/5.3 nmol/l at 13.00 h, and 2.1/2.3 nmol/l at 20.00 h, respectively. Cortisol concentrations differed between 6-7 year-old and 9 year-old children (higher in the former). Age-matched post-menarcheal girls had higher cortisol concentrations in the evening, 2.2 vs 1.7 nmol/l (p = 0.03). The results were independent of BMI, headache and allergy. In the RAP group, diurnal cortisol concentrations in girls/boys at the different time-points were 14.8/12.9, 5.2/5.8, and 2.4/2.7 nmol/l, respectively, and were negatively correlated to BMI. Total secretion of cortisol was higher than in healthy children. Cortisol concentration was independent of allergy, headache and ethnicity, CONCLUSION: In healthy children, salivary cortisol concentration was dependent on time, age and menarche. In children with RAP of psychosomatic origin, morning and total secretion of cortisol were significantly higher than in healthy children and negatively correlated to BMI.