Hypothalamic-pituitary-adrenal axis function and hypothalamic-pituitary-thyroid axis function in mentally retarded oatients with and without self-injurious and/or aggressive behaviour

English: The etiology of aggression and self-injuring behaviour in low functioning mentally retarded patients is multi-factorial and may reflect the presence of undiagnosed psychiatric conditions, unapparent due to the degree of the patient's impairment. It may also reflect hyperactivity of the stress response. The intricacies of diagnosis in this group of patients call for the development of biological markers to aid in diagnosis, therapy selection and drug response monitoring. Measuring and determining the relative contribution of individual neurotransmitters in the problem behaviour is complex and impractical. An alternative route may be to evaluate the functions of the hypothalamic-pituitary axis, which has extensive connections with the limbic area and is relatively easy to assess. The hypothalamic-pituitary system controls the behavioural, endocrine, autonomic and immunological responses to stress. The dexamethasone suppression test (OST) as adapted by Carroll and the thyroid-releasing hormone stimulation test (TRHST) has been extensively used in research on biological markers in major depression. Stress is known to activate the hypothalamic-pituitary-adrenal (HPA) axis, reflected by elevated cortisol levels. The study is a matched control study comparing hypothalamic-pituitary-adrenal axis function and hypothalamic-pituitary-thyroid axis function in 44 institutionalised mentally retarded patients with and without self-injuring and aggressive behaviour through the measurement of baseline cortisol levels and the application of the dexamethasone suppression test and the thyroid-releasing hormone stimulation test. The groups were matched according to gender, age and level of functioning. The mean age of the aggressive group 106 was 44,1 years (±SO 9,8) and the mean age of the non-aggressive group was 44,2 years (±SO 10,5). Baseline hypercortisolaemia occurred in five of the 22 aggressive subjects (22,7 %) and in two of the 22 non-aggressive subjects (9,1 %). Cortisol nonsuppression with the OST occurred in two subjects in the aggressive group (9,1 %) and one subject in the non-aggressive group (4,5 %). The OST did not demonstrate a difference in the two groups, yet there were more individuals in the aggressive group with abnormal high baseline cortisol, as well as a tendency towards a higher baseline cortisol in the aggressive group, suggesting an abnormal or more reactive stress response. Higher baseline cortisol levels were not related to age or the type of aggression, yet subjects with more recent aggressive activity showed higher baseline cortisol levels. The TRHST was generally well tolerated by the subjects. Side effects were few and transient. There were two male subjects in the aggressive group showing a blunted TRHST. Primary hypothyroidism was demonstrated in one of the female subjects in the non-aggressive group and subclinical hypothyroidism in two subjects in the non-aggressive group, as well as in one subject in the aggressive group. Longitudinal studies are needed to determine cortisol levels in unmedicated patients, in addition to comparing cortisol levels during different kinds of treatment.