The ‘stress hormone’ cortisol is extremely important for managing and regulating the body’s response to stress. Cortisol regulates metabolism, the response to stress and the immune system. The adrenal glands release cortisol, regulated by the hypothalamus and the pituitary gland in the brain.
Adrenal Glands
The paired adrenal glands live just above each kidney and are directly connected to part of the autonomic nervous system. The adrenal medulla produces adrenaline (epinephrine) and noradrenaline (norepinephrine), both of which play a role in the ‘fight or flight’ response. Read more about that system here.
The adrenal cortex produces glucocorticoids, of which cortisol is the most important. The hypothalamus regulates cortisol secretion via the HPA axis, the hypothalamus—pituitary—adrenal cortex axis. A negative feedback loop maintains cortisol at an appropriate level.
The hypothalamus releases CRH – corticotropin releasing hormone. This stimulates the anterior pituitary to secrete ACTH – adrenocorticotropic hormone. ACTH reaches the adrenal glands and causes cortisol secretion. Cortisol levels feed back into the hypothalamus and pituitary gland to reduce secretion of CRH and ACTH, keeping cortisol levels where they need to be.
Role of the HPA Axis
This system maintains homeostasis in the body by regulating metabolism, the cardiovascular system, immune system, reproductive system and the central nervous system. That’s a lot of jobs! Serious illness results from this system going wrong.
Cortisol
A glucocorticoid or ‘steroid’ hormone, cortisol is the stress hormone. It follows a diurnal cycle, increasing after waking, slowly dropping until late afternoon. It then resurges before dropping to its lowest point in the middle of the night.
Pharmaceutical versions include hydrocortisone, prednisolone and several other ‘corticosteroids’. Applications include treating inflammation, managing autoimmune disorders, chemotherapy and treating allergies.
The Effects of Cortisol
Glucose Metabolism
Cortisol stimulates glucose synthesis and the breakdown of glycogen in the muscles. It also increases the breakdown of fats and blocks insulin. It causes insulin resistance in an effort to increase blood glucose levels, i.e. blood sugar.
Immune System
Cortisol reduces the immune response, the inflammation cascade and reduces T-cell growth. That means it is immunosuppressive. This is why pharmaceutical steroids are used to treat immune-mediated and autoimmune diseases like rheumatoid arthritis, psoriasis, eczema and allergies.
Cortisol delays wound healing, because it suppresses inflammation. The inflammation process plays a role in healing of wounds, whether injuries or surgical. Steroid treatment is withdrawn prior to surgery whenever possible, for this reason.
Electrolytes and Water Homeostasis
Cortisol increases GFR (glomerular filtration rate), in other words, function of the kidneys. It causes excretion of phosphate and potassium, along with water and sodium retention. Too much cortisol or not enough cortisol will cause electrolyte disturbances.
Cortisol also stimulates secretion of stomach acid, which explains why chronic stress causes problems like heartburn and stomach ulcers. People who are stressed for a long time have high ciruclating cortisol levels.
Memory
Cortisol combined with adrenaline stimulates memories of short-term emotional evens in order to ensure we avoid the same thing in future. This effect is part of how trauma affects the mind and body in the long term. It is absolutely a factor in the development of PTSD.
Long term exposure to excess cortisol damages the hippocampus, the part of the brain essential for storing long term memories and learning. This means excess cortisol impairs the ability to learn.
Pregnancy
During pregnancy, cortisol plays two essential roles. At 30-32 weeks gestation, cortisol stimulates production of pulmonary surfactant. Surfactant allows the lungs to expand when the first breaths are taken after birth. Without it, the newborn cannot breathe. One of the byproducts of beef production is extracting this surfactant from the cow’s lungs. Cattle lung surfactant massively improved survival rates of premature babies.
The second role is to stimulate parturition, to initiate labour. Foetal cortisol triggers conversion of progesterone to oestrogen which in turn stimulates prostaglandin secretion and oxytocin receptor development. Oxytocin is the hormone that stimulates contractions of the uterus. Because it reduces progesterone, treatment with steroids can induce miscarriage in early pregnancies.
Stress
So why does this matter? The adrenal glands function to help the body cope with stressors. Adrenaline and sympathetic nervous system is there for acute dangers and cortisol is there for longer term stresses. If you are writing about someone who has been living a stressful life, they will have high levels of cortisol which impacts their physiology.
Cortisol increases insulin resistance and thus contributes to potential risk factors for type 2 diabetes mellitus. Research into this is ongoing and while stress or high cortisol alone isn’t enough to cause diabetes, it could be part of the complex of risk factors.
Cortisol affects the immune system and impacts immune-mediated disease. Interestingly, cortisol can both suppress the immune system and over-activate it. We know that stress impacts autoimmune diseases.
The HPA axis is regulated by dopamine, serotonin and norepinephrine – neurotransmitters responsible for regulating mood and emotions. This connection shows how psychological stress impacts our physiology, and vice versa.
Oxytocin down-regulates the HPA axis, reducing stress. Oxytocin is the ‘love hormone’, aside from its role in giving birth and milk let down in animals, it is released when we are close with people we love, including hugging and even during orgasm. So it proves that spending time with those we are close to can help reduce stress. This even applies to our pets!
I talked previously about the term ‘psychosomatic’ discussed in the medical terminology series. Psychosomatic means that psychiatric changes, such as mental health disorders, have an impact on our physical bodies. It does not mean that your problems are ‘all in your head’ and not real. They are real, and mental distress has an impact on our physiology too.
Proudly powered by WordPress
Discover more from Emma Stewart Writes
Subscribe to get the latest posts sent to your email.