Introduction: Higher evening cortisol level has been previously described in very preterm infants, possibly reflecting increased Hypothalamic-Pituitary-Adrenal Axis (HPA) tone or alterations in HPA regulation throughout the day. These relatively subtle differences in HPA axis function in preterm compared to full-term children may become meaningful in terms of metabolic risk later in life if sustained over time. Still, only a few studies have investigated whether altered reprogramming of the HPA axis persists beyond toddler age.
Objective: To compare salivary cortisol and cortisone levels and their circadian rhythm between very preterm and term school-aged children, all born adequate for gestational age.
Methods: In this cross-sectional study, 69 very preterm (< 32 gestational weeks) and 42 full-term (> 37 gestational weeks) school-aged children (4.9 to 8.9 years old) were included. Cortisol and cortisone concentrations in saliva, collected in the morning, at mid-day, afternoon, and before bedtime, were measured by mass spectrometry.
Results: Cortisol and cortisone levels and profiles were similar in preterm and full-term children, albeit full terms had slightly higher salivary cortisol at bedtime compared to very preterm children.
|Very preterm infant (n = 69)||Full-term infants (n = 42)||P-value|
|Salivary cortisol ug/dl median (SD)|
|Morning 08:00 am||0.18 (0.12)||3 *||0,19 (0,14)||1*||0.86|
|Mid-day||0.057 (0.036)||6*||0,075 (0,06)||3*||0.38|
|Afternoon||0.04 (0.05)||19*||0.048 (0.04)||10*||0.12|
|Bedtime||0.038 (0.54)||48*||0.059 (0.10)||22*||0.03|
|Salivary cortisone ug/dl median (SD)|
|Morning 08:00 am||0.82 (0.38)||0||0.81 (0.49)||0||0.76|
|Mid-day||0.39 (0.17)||0||0.42 (0.20)||0||0.51|
|Afternoon||0.25 (0.20)||0||0.30 (0.18)||1**||0.09|
|Bedtime||0.18 (0.23)||0||0.23 (0.3)||0||0.09|
|*Number of participants with low level of cortisol concentration below the limit of detection ** Number of participants with low level of cortisone concentration below the limit of detection Conversion units to nmol/l = ug/dl x 27.59|
Conclusion: According to our data, very preterm and full-term school children adequate for gestational age showed preserved cortisol and cortisone rhythm. Also, both groups had similar levels of these hormones at each evaluated time during the day. Considering that an important proportion of cortisol concentrations in saliva are below the detection limit, cortisone measurement is more suitable for circadian rhythm studies in this type of sample.
22 Sep 2021 - 26 Sep 2021