Pineal and pituitary-adrenocortical function in physiological aging and in senile 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 pathological brain aging.A selective impairment of the nocturnal melatonin secretion has been observed 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 significantly reduced in relation either to age or to cognitive impairment. By comparison to vascular dementia, patients with Alzheimer's disease exhibited the highest cortisol concentrations throughout the 24h. The sensitivity of the hypothalamic-pituitary-adrenal axis to the steroid feedback was significantly impaired in old subjects and particularly in the demented ones. The serum DHEAS levels were significantly lower in elderly subjects and even more in demented patients than in young controls. Consequently, a significant increase of the cortisol/DHEAS molar ratio was evident when going from young controls to healthy elderly subjects and to demented patients. In conclusion, the aging process affects many neuroendocrine functions resulting in subtle but clinically relevant consequences; the occurrence of senile dementia seems to play an additive role.