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Age-Related Changes in Fasting Plasma Cortisol in Rhesus Monkeys: Implications of Individual Differences for Pathological Consequences

¹ Obesity and Diabetes Research Center, University of Maryland School of Medicine, Baltimore.
² Biomedical Sciences and Pathobiology Department, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg.

Address correspondence to Joseph M. Erwin, PhD, Obesity and Diabetes Research Center, University of Maryland School of Medicine at Baltimore, 10 South Pine St., MSTF Rm. 6-00, Baltimore, MD 21201-1192. E-mail: jerwin{at}agingapes.org

Elevated cortisol may damage receptor neurons involved in responses to stress, leading to progressive metabolic dysregulation and age-related increases in cortisol; however, documentation of rising cortisol with age in humans has been inconsistent. Here we report fasting cortisol values from rhesus monkeys maintained for obesity, diabetes, and aging research. A modest correlation (r =.20) between age and cortisol was found for 138 rhesus monkeys (aged 4–40 years) and (r =.16) for 30 males for whom at least 10 years of longitudinal data were available. Subgroups of ad libitum-fed and weight-stabilized animals also exhibited significant positive relationships between age and cortisol (r =.14–.37). Individual regression analyses revealed both significant increases (r =.29–.85) and decreases (r = –.47 to –.66) in cortisol relative to age. Unexpectedly, significant age-related increases occurred in 77% of healthy primates, but only 33% of diabetic primates, while significant declines occurred only in diabetics.