HPA axis responsivity to dexamethasone and cognitive impairment in dementia.

1. Animal and human studies suggest a possible relationship between dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and cognitive impairment. 2. In animals, prolonged exposure to high plasma cortisol levels causes irreversible hippocampal damage. 3. Abnormal cortisol plasma levels in response to dexamethasone challenge have been frequently observed in dementia of Alzheimer's type (DAT) patients. 4. The authors studied the relationship of responsivity of the HPA axis to cognitive impairment in 34 DAT patients drug free for at least 10 days. A decrease in HPA axis responsivity significantly correlated with greater cognitive impairment.