HPA Axis (Sweis, B. M, 2012)

By J. B. Fagoyinbo

Stress causes a surge of hormones in your body (BBC, 2013; NHS Choices, 2014). These stress hormones are released to enable you to deal with pressures or threats – the so-called fight or flight response. Stress hormones such as cortisol and epinephrine are released by the body in situations that are interpreted as being potentially dangerous. The hormone regulating system is known as the endocrine system and it is made up of:

  1. Adrenaline is produced by the adrenal glands after receiving a message from the brain that a stressful situation has presented itself. Amit Sood believes the view that, along with norepinephrine, Adrenaline is largely responsible for the immediate reactions we feel when stressed (Klein, 2013). A good example is when you are about to place your foot on a foot bridge across a deep fast-flowing river only for a lightning to reveal that what you think is a bridge is a floating debris. You withdraw your foot and your heart pounds. Your muscles are tense, you’re breathing faster, you may start sweating. That’s adrenaline. Along with the increase in heart rate, adrenaline also gives you a surge of energy — which you might need to run away from a dangerous situation — and also focuses your attention.
  2. Norepinephrine is similar to adrenaline, released from the adrenal glands and also from the brain. The primary role of norepinephrine, like adrenaline, is arousal. “When you are stressed, you become more aware, awake, focused,” Amit Sood says. “You are just generally more responsive.” It also helps to shift blood flow away from areas where it might not be so crucial, like the skin, and toward  essential areas at the time, like the muscles, so you can flee the stressful scene. Although norepinephrine might seem redundant given adrenaline (which is also sometimes called epinephrine), Sood imagines we have both hormones as a type of backup system. “Say your adrenal glands are not working well,” he says. “I still want something to save me from acute catastrophe.” Depending on the long-term impact of whatever is stressing you out — and how you personally handle stress — it could take anywhere from half an hour to a couple of days to return to your normal resting state, says Sood.
  3. Cortisol is a steroid hormone, commonly known as the stress hormone, produced by the adrenal glands. While adrenaline arms you to fight or run, cortisol functions to maintain adequate body fluids and salts, blood pressure and other vital systems in a normal range. Death may result the cortisol cannot increase enough to meet the level of stress, such as the stress of surgery. Cortisol is relatively slow acting; it takes a little more time for you to feel the effects of cortisol in the face of stress because the release of this hormone takes a multi-step process involving two additional minor hormones.First, the part of the brain called the amygdala has to recognize a threat. It then sends a message to the part of the brain called the hypothalamus, which releases corticotropin-releasing hormone (CRH). CRH then tells the pituitary gland to release adrenocorticotropic hormone (ACTH), which tells the adrenal glands to produce cortisol. Edwards (2005) illustrates this with the situation in which you must make an oral presentation in front of your peers. As you take your place before the group, your heart pounds in your chest, your palms become sweaty, and your knees shake uncontrollably. In short, you are stricken with fear, a strong emotion caused by the threat of danger or something unwelcome happening. Amit Sood explains that the body’s alarm circuit for fear lies in an almond-shaped mass of nuclei deep in the brain’s temporal lobe (Klein, 2013). In survival mode, the optimal amounts of cortisol can be lifesaving. It helps to maintain fluid balance and blood pressure, while regulating some body functions that aren’t crucial in the moment, like reproductive drive, immunity, digestion and growth. Amit Sood, however, warns that when you stew on a problem, the body continuously releases cortisol, and chronic elevated levels can lead to serious issues. Too much cortisol can suppress the immune system, increase blood pressure and sugar, decrease libido, produce acne, contribute to obesity and more.

Amit Sood adds that estrogen and testosterone are also hormones (hormones involved in the growth, maintenance, and repair of reproductive tissues) that affect how we react to stress, as are the neurotransmitters dopamine and serotonin responsible for communicating information throughout our brain and body. But the classic fight-or-flight reaction is mostly due to the three major players mentioned above. How do you react to stress? Let us know in the comments.


BBC (2013). What is stress? Accessed 29 Aug 2015

Edwards, S. P. (2005). The Amygdala: The Body’s Alarm Circuit : The Body’s Alarm Circuit. May 2005. The Dana Foundation

Klein, S. (2013). Adrenaline, Cortisol, Norepinephrine: The Three Major Stress Hormones, Explained. The Huffington Post (19 Apr 2013).

NHS Choices (2014). Struggling with stress? In  Stress, anxiety and depression. Accessed 29 Aug 2015.

Ratini, M. (2014). Normal Testosterone and Estrogen Levels in Women.  WebMD Medical Reference. November 21, 2014

Ruddock, V. Undated (). What Are Stress Hormones? Accessed 29 Aug 2015.

About jbfagga 42 Articles
Engr Joseph Babatunde Fagoyinbo was born on January 16, 1947. He enlisted for engineering education and obtained the BSc degree in Agricultural Engineering in 1977 and an M.Eng degree in Environmental Engineering in 1982. He attended an 8-week training programme at the Fondation de l’Eau, Limoges France in July/August 1998 as the leader of a Nigerian delegation. In 2000 he also attended the UNESCO-sponsored Higher Hydrologicy Course at the Moscow State University in July/August 2000 Engr Fagoyinbo has since 1977 been having practsing in the field of engineering including design and construction supervision of water supply, river channel training works and environmental management facilities, industrial development, entrepreneurship, etc.

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