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

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


          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.


          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.


          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.

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          Most cited references 41

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          The genetics of mammalian circadian order and disorder: implications for physiology and disease.

          Circadian cycles affect a variety of physiological processes, and disruptions of normal circadian biology therefore have the potential to influence a range of disease-related pathways. The genetic basis of circadian rhythms is well studied in model organisms and, more recently, studies of the genetic basis of circadian disorders has confirmed the conservation of key players in circadian biology from invertebrates to humans. In addition, important advances have been made in understanding how these molecules influence physiological functions in tissues throughout the body. Together, these studies set the scene for applying our knowledge of circadian biology to the understanding and treatment of a range of human diseases, including cancer and metabolic and behavioural disorders.
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            Genetics of autism: complex aetiology for a heterogeneous disorder.

            Since autism was first recognized as a disorder in 1943, speculation about its aetiology has ranged from biological to psychological and back again. After twin studies during the 1970s and 1980s yielded unequivocal evidence for a genetic component, aetiological research in autism began to focus primarily on uncovering the genetic mechanisms involved. The identification of chromosomal abnormalities and Mendelian syndromes among individuals with autism, in conjunction with data from genome screens and candidate-gene studies, has helped to refine the view of the complex genetics that underlies autism spectrum conditions.
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              Developmental changes in brain serotonin synthesis capacity in autistic and nonautistic children.

              Serotonin content, serotonin uptake sites, and serotonin receptor binding measured in animal studies are all higher in the developing brain, compared with adult values, and decline before puberty. Furthermore, a disruption of synaptic connectivity in sensory cortical regions can result from experimental increase or decrease of brain serotonin before puberty. The purpose of the present study was to determine whether brain serotonin synthesis capacity is higher in children than in adults and whether there are differences in serotonin synthesis capacity between autistic and nonautistic children. Serotonin synthesis capacity was measured in autistic and nonautistic children at different ages, using alpha[11C]methyl-L-tryptophan and positron emission tomography. Global brain values for serotonin synthesis capacity (K complex) were obtained for autistic children (n = 30), their nonautistic siblings (n = 8), and epileptic children without autism (n = 16). K-complex values were plotted according to age and fitted to linear and five-parameter functions, to determine developmental changes and differences in serotonin synthesis between groups. For nonautistic children, serotonin synthesis capacity was more than 200% of adult values until the age of 5 years and then declined toward adult values. Serotonin synthesis capacity values declined at an earlier age in girls than in boys. In autistic children, serotonin synthesis capacity increased gradually between the ages of 2 years and 15 years to values 1.5 times adult normal values and showed no sex difference. Significant differences were detected between the autistic and epileptic groups and between the autistic and sibling groups for the change with age in the serotonin synthesis capacity. These data suggest that humans undergo a period of high brain serotonin synthesis capacity during childhood, and that this developmental process is disrupted in autistic children.

                Author and article information

                Croat Med J
                Croat. Med. J
                Croatian Medical Journal
                Croatian Medical Schools
                February 2013
                : 54
                : 1
                : 33-41
                [1 ]Department of Biochemistry, Bharathi Women’s College, University of Madras, Chennai, Tamil Nadu, India
                [2 ]Madras Medical College and Pediatrician Institute of Child Health and Hospital for Children, Chennai, Tamil Nadu, India
                Author notes
                Correspondence to: 
Geetha Arumugam
Department of Biochemistry
Bharathi Women’s College (Affiliated to University of Madras)
North Chennai – 600 108, Tamil Nadu, India
                Copyright © 2013 by the Croatian Medical Journal. All rights reserved.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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