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

Divisions of 1 Endocrinology and Metabolism and 2 Gerontology and Geriatrics, Departments of Medicine, Johns Hopkins Bayview Medical Center and Johns Hopkins University School of Medicine and 3 Endocrinology Section, Laboratory of Clinical Investigation, Intramural Research Program, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224; and 4 Division of Endocrinology and Metabolism, Department of Medicine, University of Virginia Health System, Charlottesville, Virginia 22908 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 steroid levels to assess the interrelationships between cortisol and growth hormone (GH) secretion and whether these relationships differ by sex. Blood was sampled every 20 min from 8:00 PM to 8:00 AM; cortisol was measured by RIA 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