The endocrine system refers to that functional part of the body responsible for the production of hormones -- substances that have effects on target organs some distance away from where the hormones are made. Physical exercise would be impossible without the contribution of hormones. On the other hand, exercise can have profound effects on the endocrine system. Therefore, the interplay between the endocrine system and physical training is complex.
Adrenal Axis
The adrenal gland produces "adrenalin" (norepinephrine) as well as cortisol and the hormone that regulates it via the pituitary gland, ATCH. Norepinephrine lies at the center of the "fight-or-flight" response, whereas cortisol is released in response to stress and suppresses the immune system. A 2002 study published in the June issue of "Aviation, Space, and Environmental Medicine" found that seven days of very intense exercise significantly elevated levels of cortisol and ACTH, suggesting that the study subjects were highly stressed and perhaps "overworked."
Androgens
Some weightlifters and professional athletes use anabolic steroids to boost strength and improve performance. These substances are the artificial counterparts of the sex hormone testosterone. Testosterone is a vital hormone in various modes of exercise and contributes to muscle mass and strength. A 2009 study by Te-Chi Liu et al. in "Adaptive Medicine" revealed that a single session of exercise results in a rapid rise in serum levels of testosterone, and that the degree of increase correlates with the type, duration and intensity of exercise.
Thyroid Hormones
Thyroid hormone, produced in the thyroid gland below the neck, plays important roles in a host of metabolic functions, influencing growth, tissue differentiation, fatty acid use and temperature regulation. A shortage of the hormone often results in weight gain and general lassitude. A 2005 study published in "Neuroendocrinology Letters" found that moderate to very intense aerobic exercise produced a significant rise in circulating thyroid hormone levels, and that the degree of this increase was correlated with intensity level.
Pancreatic Hormones
The pancreas produces insulin, a hormone essential for keeping blood glucose levels in a normal range by promoting the uptake of glucose into body tissues. It also produces glucagon, the actions of which oppose those of insulin and lead to release of glucose from body tissues. A 1986 study by J.J. Wolfe and colleagues demonstrated that during light exercise, both a rise in glucagon level and a drop in insulin level are necessary to maintain blood glucose in a normal range.
References
- "Aviation, Space, and Environmental Medicine"; Pituitary-Adrenal and Pituitary-Thyroid Hormone Responses During Exercise-Cold Exposure After 7 Days of Exhaustive Exercise; J.W. Castellani et al.; June 2002
- "Adaptive Medicine"; Exercise and Testosterone; Te-Chi Liu, Chia-Hua Kuo and Paulus S. Wang; August 31, 2009
- "Neuroendorinology Letters"; Exercise Intensity and its Effect on Thyroid Hormones; Figen Ciloglu et al.; December 2005
- "Journal of Clinical Investigation"; Role of Changes in Insulin and Glucagon in Glucose Homeostasis in Exercise; J. J. Wolfe et al.; March 1986
