Activity in the hypothalamic-pituitary-adrenal axis and delirium.

Glucocorticoid hormones are important for coping with stress but may have deleterious effects on mood and memory during prolonged excessive secretion. A key abnormality related to cortisol excess in delirium seems to be abnormal 'shut-off' of the hypothalamic-pituitary-adrenal (HPA) axis tested by the dexamethasone suppression test. In experimental models, the hippocampal formation is of prime importance for normal HPA axis shut-off. In this brain area, a close interaction between neurotransmittors, notably acetylcholine, serotonin and noradrenaline, and glucocorticoid receptors, is present and possibly relevant for the development of delirium in elderly patients with stroke and neurodegenerative brain diseases.