JOURNAL OF BIOLOGICAL REGULATORS & HOMEOSTATIC AGENTS Vol. 23, no. 1, 15-22 (2009) 0393-974X (2009) Copyright © by BIOLIFE, s.a.s. This publication and/or article is for individual use only and may not be further reproduced without written permission from the copyright holder. Unauthorized reproduction may result in fnancial and other penalties 15 SERUM MELATONIN CONCENTRATION IN THE CHILD WITH NON-ORGANIC FAILURE TO THRIVE: COMPARISON WITH OTHERS TYPES OF STRESS A. MUÑOZ-HOYOS, A. MOLINA-CARBALLO, J. UBEROS, F. CONTRERAS-CHOVA, M. DEL CARMEN AUGUSTIN-MORALES, M. RUIZ-ALBA, and G. GALDÓ-MUÑOZ Unidad de Gestión Clínica de Pediatría, Hospital Universitario San Cecilio de Granada, Universidad de Granada, Granada, Spain Received August 20, 2008 – Accepted January 28, 2009 Human beings must adapt both to novel, unfavourable conditions and to circumstances of physical or psychological isolation. The initial response to stress depends fundamentally on the activation of the HPA axis. In regaining homeostatic equilibrium, melatonin plays a role due to its synchronising and anti- stress properties. To study the role of melatonin and the pineal gland in the organic and/or behavioural response to acute or chronic stress, 311 children were divided into two large groups: 1) Control Group - 121 healthy children classifed, in turn, into 4 control subgroups, one for each pathology being studied; 2) Problem Groups, classifed as traumatic stress (n=58), surgical stress (n=38), psychic stress (n=64) and febrile stress (n=30), according to pre-established clinical criteria. These groups were sub-classifed according to the degree (low or high) and duration (acute or chronic) of the stress. This study used a case controlled, cross sectional design. Serum melatonin was measured by radioimmunoassay (RIA). In all the situations of acute stress, melatonin increased at a rate directly proportional to the severity and/ or duration of the stress-causing stimulus. In contrast, in chronic stress, i.e. the Affective Deprivation Syndrome (or Psychological Dwarfsm) with or without non-organic failure to thrive, resulted in the opposite response with a signifcant reduction of melatonin. In conclusion, in acute stress an increase in the bioavailability of melatonin could contribute to maintaining homeostatic balance. The lack of an appropriate response to acute stress could make some groups of patients (Affective deprivation syndrome with or without growth failure) predisposed to suffer depressive symptoms associated with a wide range of neurological, endocrinological or immunological consequences. Mailing address:Dr. D. Antonio Molina-Carballo, Departamento de Pediatría, Facultad de Medicina, Avda. de Madrid 11, E 18012 Granada, Spain Tel: ++34 958023996. Fax: ++34 958240740. e-mail: amolinac@ugr.es Key words: melatonin, children, acute stress, febrile stress, surgery stress, traumatic stress, affective deprivation syndrome, non-organic failure to thrive syndrome, low melatonin syndrome Human beings must adapt to novel, unfavourable conditions or to circumstances of physical or psychological isolation. This homeostatic response is known as the stress reaction (1). Glucocorticoids and cytokines are important mediators of injury responses (2). It has been suggested that glucocorticoids and central/peripheral cytokines are fnely balanced to maintain homeostasis with reciprocal inhibition/ activation pathways being present (3). Because of their potent activatory effect on the HPA axis, proinfammatory cytokines could contribute to the elevated levels of glucocorticoids that are observed