title: Ultradian plasma corticotropin and cortisol rhythms: time-series analyses.
abstract: 24-h plasma patterns of ACTH and cortisol were established in 6 subjects who had standard meals and in 4 subjects under continuous enteral nutrition. Temporal relationships between both hormones were analyzed. The individual assay data were subjected to time-series analyses to identify the periods of the oscillations in the plasma levels. The spontaneously occurring cortisol peaks were preceded by increases in ACTH levels, but z-score transformations clearly revealed that ACTH and cortisol were not quantitatively linked throughout the day. Individual subjects' power spectra gave evidence of a predominant periodicity in the oscillations of both hormones. These periodicities varied between individuals. They were 55-140 min for ACTH and 95-180 min for cortisol, indicating that, on occasion, a single cortisol peak may be initiated by two ACTH peaks. Cross spectral analysis of the individual data gave coherence spectra with a large peak which accounted for a substantial concordance of their period length, and cross variance spectra showed a consistent phase relationship between both hormones. These time series analyses applied to the data further support the concept that ACTH is the stimulating factor of cortisol release under basic conditions.
mesh_terms: D000204:Activity Cycles; D000324:Adrenocorticotropic Hormone / Q000097:blood*; D002940:Circadian Rhythm; D004435:Eating; D004750:Enteral Nutrition; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male
chemical_list: D000324:Adrenocorticotropic Hormone; D006854:Hydrocortisone