ESPE Abstracts

In adults and older children with adrenal insufficiency, hydrocortisone replacement therapy is based on the assumption that the secretion of cortisol follows a diurnal pattern, with a peak in the early morning, a gradual decline over the day and a nadir at midnight. However, replacement therapy with multiple daily doses of hydrocortisone is unable to exactly match the normal diurnal rhythm of cortisol secretion from an intact hypothalamus-pituitary-adrenal (HPA) axis, with consequences for metabolism. In infants with adrenal insufficiency mismatch between hydrocortisone dosing scheme and cortisol clock may be even more prominent because of lack of normative data for HPA axis rhythmicity, while its consequences may be larger, considering that in infancy metabolic set point are set for life. Some studies suggest that a rhythm in HPA axis activity might already be present in the fetus, with data showing that markers of the fetal adrenal zone were higher in the afternoon than at other times of the day. However, the exact age at which an adult-type rhythm in cortisol secretion is established, could not be pinpointed, because studies conducted to date took too few samples across the diurnal cycle for the study of HPA axis rhythmicity. Based on the currently available scattered data it is assumed that an adult-type rhythm of cortisol secretion is established somewhere between 2 weeks and 9 months of age. During this talk novel data on HPA axis rhythmicity development will be presented.