Cortisol

Description
Cortisol is a steroid hormone produced by the adrenal cortex. As a stress induced hormone, cortisol secretion to an immediate challenge is a healthy response, while consistently high cortisol reactivity to repeated familiar challenges is an atypical response that may reflect chronic physiological stress (Epel et al., 2000) and is associated with negative health outcomes in old age (Seeman et al., 1997).

Cortisol has a strong diurnal variation, generally high early in the morning and falling during the day. Cortisol typically increases over the first few minutes of the day, reaching a peak 20-30 minutes after waking (http://labtestsonline.org/understanding/analytes/cortisol/test.html).

Levels of cortisol and its antagonist dehydroepiandrosterone sulfate (DHEAS) are indicators of HPA activity. As an individual interacts with his/her environment, the stimuli encountered can serve as challenges or stressors that elicit responses from the HPA axis as well as other internal homeostatic regulatory systems. Heat, cold, infection, trauma, exercise, obesity, pregnancy, and debilitating disease influence cortisol secretion (http://labtestsonline.org/understanding/analytes/cortisol/test.html).

Drugs that can increase cortisol measurements include estrogen and synthetic glucocorticoids, like prednisone and prednisolone (http://labtestsonline.org/understanding/analytes/cortisol/test.html). Drugs that can decrease cortisol measurements include androgens and phenytoin (http://labtestsonline.org/understanding/analytes/cortisol/test.html).

Significance of Measurement
Cortisol levels have been shown to be greater among individuals experiencing chronic stress from work or emotional strain (Steptoe et al., 2000).

Health consequences of exposure to elevated cortisol include increased cardiovascular risk (Henry, 1983), poorer cognitive functioning (Lupien et al., 1994; Seeman et al., 1997), and increased risks for fractures (Greendale et al., 1999). Higher levels of urinary catecholamine excretion have also been shown to predict functional disability and mortality (Reuben et al., 2000).

Method of Measurement
Cortisol level is usually assessed using a blood test, however it can be measured using saliva or urine. Urine is collected over a 12 or 24-hour period in order to represent a daily level. Researchers can be interested in the profile of cortisol change over the day; or change in the cortisol level after waking in the morning or the pattern of change over the day. To determine cortisol pattern over the day, it may be measured as much as four or fie time times – upon waking, shortly afterward, afternoon, evening and night.

Normal levels of cortisol in the bloodstream range from 6-23 mcg/dl (micrograms per deciliter). Normal 24-hour urinary cortisol levels range from 10-100 micrograms/ 24 hours (http://labtestsonline.org/understanding/analytes/cortisol/test.html).

In the MacArthur Study the cut off of urinary cortisol was =25.69 ug/g creatinine (Seeman et al., 2004).

References
· Epel, E.S., McEwen, B., Seeman, T., Matthews, K., Castellazzo, G., Brownell, K.D., et al. (2000). Stress and body shape: Stress-induced cortisol secretion is consistently greater among women with central fat. Psychosomatic Medicine, 62(5), 623-632.
· Greendale, G., Unger, J.B., Rowe, J.W., & Seeman, T. (1999). The relation between cortisol excretion and fractures in healthy older people: Results from the MacArthur Studies of Successful Aging. Journal of the American Geriatrics Society, 47(7), 799-803.
· Henry, J. (1983). Coronary heart disease and arousal of the adrenal cortical axis. In T. Dembrosk, T. Schmidt, & G. Blumchen (Eds.), Biobehavioral Bases of Coronary Heart Disease (pp. 365-381). Basel: Karger. .
· Lab Tests Online. (2004). Cortisol. Retrieved March 25, 2005, from http://labtestsonline.org/understanding/analytes/cortisol/test.html).
· Lupien, S., LeCours, A., Lussier, I., Schwartz, G., Nair, N., & Meaney, M. (1994). Basal cortisol levels and cognitive deficits in human aging. Journal of Neuroscience, 14, 2893-2903.
· Reuben, D.B., Talvi, S.L., Rowe, J.W., & Seeman, T.E. (2000). High urinary catecholamine excretion predicts mortality and functional decline in high-functioning, community-dwelling older persons: MacArthur Studies of Successful Aging. Journal of Gerontology: Medical Sciences, 55(10), M618-M624.
· Seeman, T.E., Crimmins, E., Huang, M.H., Singer, B., Bucur, A., Gruenewald, T., et al. (2004). Cumulative biological risk and socio-economic differences in mortality: MacArthur studies of successful aging. Social Science and Medicine, 58(10), 1985-1997.
· Seeman, T., McEwen, B., Singer, B., Albert, M., & Rowe, J. (1997). Increase in urinary cortisol excretion and declines in memory: MacArthur Studies of Successful Aging. Journal of Clinical Endocrinology and Metabolism, 82, 2458-2465.
· Steptoe, A., Cropley, M., Griffith, J., & Kirschbaum, C. (2000). Job strain and anger expression predict early morning elevations in salivary cortisol. Psychosomatic Medicine, 62, 286-292.
· Please refer to the Research Network on Socioeconomic Status and Health website for details. http://www.macses.ucsf.edu/Research/Allostatic/notebook/salivarycort.html