Abnormal circadian rhythm and cortisol excretion in autistic children: a clinical study.

Aim: To determine the circadian rhythm alteration of cortisol excretion and the level of corticosteroids in children with different grades of autism severity.

Methods: The study included 45 children with different grades of autism severity (low [LFA], medium [MFA], and high functioning autism [HFA]), 15 in each group, and 45 age/sex-matched children with typical development. The urinary levels of free cortisol (at three phases of 24-hour cycle), corticosteroids, vanilylmandelic acid, and 5-hydroxyindole acetic acid were determined.

Results: Alteration in the pattern of cortisol excretion (Phases I, II, and III) was observed in children with LFA (Phase I: 43.8 ± 4.43 vs 74.30 ± 8.62, P=0.000; Phase II: 21.1 ± 2.87 vs 62 ± 7.68, P<0.001; Phase III: 9.9 ± 1.20 vs 40 ± 5.73, P<0.001) and MFA (Phase I: 43.8 ± 4.43 vs 52.6 ± 7.90, P<0.001; Phase II: 21.1 ± 2.87 vs 27.4 ± 4.05, P<0.001; Phase III: 9.9 ± 1.20 vs 19 ± 2.50, P<0.001) compared to the control group. The corticosteroids excretion levels were higher in all the groups of children with autism than in the control group. The level of 5-hydroxyindole acetic acid was significantly higher in children with LFA (8.2 ± 1.48 vs 6.8 ± 0.85, P<0.001) and MFA (8.2 ± 1.48 vs 7.4 ± 0.89, P=0.001) and not significantly higher in children with HFA than in the control group. The changes were correlated with degrees of severity of the disorder.

Conclusion: These data suggest that altered cortisol excretion pattern and high level of corticosteroids in urine may probably be a consequence of altered hypothalamic-pituitary-adrenal axis function, which may contribute to the pathogenesis and affect the severity of autism.