Cortisol and GH secretory dynamics, and their interrelationships, in healthy aged women and men

We studied 130 healthy aged women (n = 57) and men (n = 73), age 65-88 yr, with age-related reductions in insulin-like growth factor I and gonadal ste roid levels to assess the interrelationships between cortisol and growth ho rmone (GH) secretion and whether these relationships differ by sex. Blood w as sampled every 20 min from 8:00 PM to 8:00 AM; cortisol was measured by R IA and GH by immunoradiometric assay, followed by deconvolution analyses of hormone secretory parameters and assessment of approximate entropy (ApEn) and cross-ApEn. Cortisol mass/burst, cortisol production rate, and mean and integrated serum cortisol concentrations (P < 0.0005), and overnight basal GH secretion (P < 0.05), were elevated in women vs. men. Integrated cortis ol concentrations were directly related to most measures of GH secretion in women (P < 0.01) and with mean and integrated GH concentrations in men (P, 0.05). Integrated GH concentrations were directly related to mean and inte grated cortisol levels in women (P < 0.005) and men (P, 0.05), with no sex differences. There were no sex differences in cortisol or GH ApEn values; h owever, the cross-ApEn score was greater in women (P, 0.05), indicating red uced GH-cortisol pattern synchrony in aged women vs. men. There were no sig nificant relationships of integrated cortisol secretion with GH ApEn, or vi ce versa, in either sex. Thus postmenopausal women appear to maintain eleva ted cortisol production in patterns that are relatively uncoupled from thos e of GH, whereas mean hormone outputs remain correlated.