Pineal and pituitary-adrenocortical function in physiological aging and insenile dementia

The simultaneous evaluation of the circadian rhythm of plasma melatonin and ACTH and of serum cortisol and DHEAS represents a clinically reliable tool to appreciate the neuroendocrine changes occurring in physiological and pa thological brain aging. A selective impairment of the nocturnal melatonin secretion has been observ ed in elderly subjects, being significantly related either to the age or to the severity of dementia. A significant increase of serum cortisol levels during evening- and night-times was found in elderly subjects, particularly if demented, when compared to young controls. Besides, both the circadian amplitude of cortisol rhythm and the nocturnal cortisol increase were signi ficantly reduced in relation either to age or to cognitive impairment. By c omparison to vascular dementia, patients with Alzheimer's disease exhibited the highest cortisol concentrations throughout the 24 h. The sensitivity o f the hypothalamic-pituitary-adrenal axis to the steroid feedback was signi ficantly impaired in old subjects and particularly in the demented ones. Th e serum DHEAS levels were significantly lower in elderly subjects and even more in demented patients than in young controls. Consequently, a significa nt increase of the cortisol/DHEAS molar ratio was evident when going from y oung controls to healthy elderly subjects and to demented patients. In conclusion, the aging process affects many neuroendocrine functions resu lting in subtle but clinically relevant consequences; the occurrence of sen ile dementia seems to play an additive role. (C) 2000 Elsevier Science Inc. All rights reserved.