Effects of ageing on endocrine and neuroendocrine rhythms in humans

Biological rhythms in blood variables are now fairly well documented in young healthy adults whereas reports in elderly subjects are few for obvious reasons including the difficulty of setting up a group of elderly subjects comparable in age and social background and moreover free of major liver, heart, kidney, bone or any other degenerative disease and consequently not requiring medication. We have observed that the parameters characteristic of the biological rhythm may be modified with ageing. However, the modifications are different from one function or variable to the next. Differences in acrophases, mesors and amplitudes could be demonstrated. For instance the acrophase may be phase-advanced in the elderly for plasma cortisol, DHEA-S, 18-OHDOC, the amplitude may be modified for testosterone, 18-OHDOC, proteins, melatonin, gonadotrophins. The administration as a function of time of drugs or agents used as a diagnostic tool made it possible to ascertain the importance of the time structure in this field. Both validity and interpretation of such administration depend upon the timing of the agent administration in the 24-hour scale. Therefore, the temporal organization of the subjects undergoing such treatments should be taken into account. In the near future this kind of investigation on various biological variables may lead to an improvement of the desired drug effects in elderly patients.