Epinephrine

Description
Epinephrine, a stress hormone important to the body’s metabolism, is also known as adrenaline. Heightened secretion caused perhaps by fear or anger, will result in increased heart rate and the hydrolysis of glycogen to glucose. This reaction, often called the “fight or flight” response, prepares the body for strenuous activity (http://www.nlm.nih.gov/medlineplus/ency/article/003613.htm). Epinephrine, part of a family of catecholamines, together with norepinephrine, is secreted principally by the medulla of the adrenal gland.
(http://www.encyclopedia.com/html/e1/epinephr.asp). Plasma levels of catecholamines may be influenced by a variety of postural, diurnal, and acute stress-related factors (Young & Landsberg, 1998)

Significance of Measurement
Increases over time in urinary excretion of epinephrine predicts subsequent cognitive decline in older men (Karlamangla et al., 2005). High plasma epinephrine has been associated with poor survival rate in patients with previous myocardial infarction (Goldstein, 1984) but increased survival among healthy older persons (Christensen, & Schultz-Larsen, 1994). Urinary epinephrine excretion is significantly lower among women and among subjects with a BMI >27 (Reuben et al., 2000). Current smokers have higher levels of both urinary norepinephrine and epinephrine (Reuben et al., 2000).

Method of Measurement
Epinephrine is excreted with the urine. Because levels vary over the day, 12 hour or 24 hour urine collections are used. Values can be normalized by creatinine excretion to adjust for body size (Karlamangla et al., 2005). To adjust for body size, results for epinephrine are reported as micrograms of epinephrine per gram creatinine of urine excretion (Reuben et al., 2000). Determinations can be made with high-pressure liquid chromatography (Krsulovic, 1983).

There are no normative values for urinary epinephrine levels but researchers have classified them relatively using quartiles or tertiles for individual samples. The MacArthur study used a cut off of greater than 4.99 ug/g creatinine for high risk epinephrine.

Epinephrine may also be determined from a blood plasma test. Although this is used more rarely.

References
· Christensen, N.J., & Schultz-Larsen, K. (1994). Resting venous plasma adrenalin in 70-year men correlated positively to survival in a population study. Journal of Internal Medicine, 235, 229-232.
· Encychopeida.com. (2005). Epinephrine. Retrieved from March 28, 2005, from http://www.encyclopedia.com/html/e1/epinephr.asp
· Goldstein, D.S. (1984). Plasma catecholamines in clinical studies of cardiovascular diseases. Acta Physiologica Scandinavica, 527(supple), 39-41.
· Karlamangla, A.S., Singer, B.H., Greendale, G.A., & Seeman, T.E. (2005). Increase in epinephrine excretion is associated with cognitive decline in elderly men: MacArthur studies of successful aging. Psychoneuroendocrinology, 30(5), 453-460.
· Krsulovic, A.M. (1983). Investigations of catecholamine metabolism using high performance liquid chromatography: Analytical methodology and clinical applicators. Journal of Chromatography, 9, 1-34.
· 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.
· U.S. National Library of Medicine & National Institutes of Health. (2003). Medline plus: Trusted health information for you. Retrieved March 28, 2005, from http://www.nlm.nih.gov/medlineplus/ency/article/003613.htm
· Young, J.B., & Landsberg, L. (1998). Catecholamines and the adrenal medulla. In J.D. Wilson, D.W. Foster, H.M. Kroenberg, & P.R. Larsen (Eds.), Williams Textbook of Endocrinology, (9th Edition, pp.665-728). Philadelphia, PA: W.B. Saunders.