The adrenal glands stand out as one of the body's smallest organs, yet perform a pivotal role in normal day-to-day living. Whether responding to stressful situations, mediating an immune system response or providing signals for digestive processes, the adrenals stay constantly involved in almost every process you may take for granted.
Physiology
Your body possesses two adrenal glands. Each forms a small, walnut-size triangle and sits atop each of your kidneys. The physiology of the adrenal glands focuses on the adrenal cortex, the outer layer that produces steroid hormones, and the adrenal medulla, the interior that controls the release of adrenaline. The adrenal cortex benefits from a rich blood supply that allows it to respond to hormonal stimuli in the bloodstream. The medulla connects to the central nervous system via the splanchic nerve, a connection that may become useful in the "fight or flight" response.
Adrenaline Release
Researchers such as Dr. Robert Kapolsky, author of the best-selling "Why Zebras Don't Get Ulcers," explain how the "fight or flight" reaction evolved to deal with instant and immediate threats. Mediated by the sudden release of adrenaline, this reaction prepares the body to run away from a potential threat or for a violent confrontation; the heart rate rises, and fatty acids and glucose flood the bloodstream and stimulate the immune system. The body can only release the adrenaline so quickly because of the way the splanchic nerve carries information about perceived threats from the brain to the adrenal medulla.
Steroid Production
As the central nervous system activates the release of adrenaline to fuel this "fight or flight" response, the brain also instigates the release of steroid hormones such as cortisol to counterbalance it. The brain achieves this by releasing a hormone called adreno-corticotrophin from the pituitary gland, which stimulates the release of cortisol from the adrenal cortex. The steroid hormone, often referred to as a glucocorticoid, offers a number of effects to counterbalance those exerted by adrenaline; cortisol increases fat storage, reduces sensory sensitivity and suppresses the immune system.
Sex Hormones
DHEA stands out as one of the other steroid hormones produced. DHEA, or duhydroepiandrosterone, works in tandem with cortisol around the body, but also serves as the precursor hormone for estrogen, testosterone and progesterone. Without DHEA, the gonads have no base substance from which to produce these sex hormones. As such, any fluctuations in the levels of DHEA affect sex drive, mental clarity and mood, as well as impairing the function of the adrenal gland.
Adrenal Dysfunction
Some extreme dysfunctions sometimes occur in the adrenal gland. Addison's disease describes the near absence of cortisol; this represents a life-threatening event for the sufferer, who may likely remain bed-bound. Cushing's disease fits the alternative pattern, with hypersecretion of cortisol. Patients with this disorder often present with fatigue and a "moon face," in which the high level of steroid hormones creates additional fat storage in the face. However, both these conditions are very rare; adrenal fatigue represents the most common dysfunction of these glands. This umbrella term emcompasses a whole range of hormonal fluctuations that may occur following a period of sustained stress, often resulting in low levels of cortisol and/or DHEA.
References
- "Why Zebras Don't Get Ulcers"; Dr. Robert Kapolsky; 2002
- Dr. Joseph Mercola: Tired all the Time?
