Chronic stress, the adrenal gland, and the HPA axis



Chances are, you've heard of adrenal fatigue...


While adrenal fatigue is not a official diagnosis (true adrenal failure is a life threatening medical emergency), the effect of chronic stress on the body is very real, and can cause distressing type symptoms often labelled as 'adrenal fatigue' or 'burnout', depending on how you view it


Not all stress is actually bad - we need a certain level of stress for our bodies to function well - things like exercise, pregnancy, cold, hunger, and illness can all trigger a stress response, which actually helps stimulate the immune system and makes the body function more effectively

But when stress becomes chronic and unrelenting, with no time for the 'stress system' to recover, it can affect almost every part of the body- metabolism, immune function, blood sugar control, gut health, brain function, and fertility just to name a few


So how does this all work?


The brain is constantly interpreting and responding to environmental cues,- these are sent to the hypothalamus, which decides whether something is a threat or not based on previous exposure and responses

The hypothalamus is influenced by the limbic system in the brain, in particular the amygdala (the 'alarm centre') which is responsible for memory, and emotion

The hypothalamus then sends signals to the pituitary gland to tell it how to respond. The pituitary gland is a tiny gland near the brain, and is the 'hormone master control centre' - it regulates multiple organ systems such as the thyroid, sex hormones, insulin levels, cortisol (stress hormone), growth, metabolism, immunity etc


If the pituitary gland receives a stress signal,- it sends ACTH hormone to the adrenal glands, which sit above the kidneys

The adrenal glands then secrete adrenaline and cortisol to signal to the rest of the body to respond to the stressor :

- adrenaline is the 'fight or flight' hormone that speeds up heart rate and breathing, increases blood pressure, and diverts blood to the brain and muscles (and away from the gut and reproductive organs) It's what gives the 'rush' feeling when you get a fright, and causes the symptoms of panic attacks. Its also what causes 'butterflies' in the stomach, and can trigger off the need to go to the bathroom when stressed (such as in irritable bowel syndrome)


- cortisol kicks in shortly after this, and sustains the stress response if it's needed for longer than a few seconds. It increases blood sugar (to provide fuel to muscles and brain), alters immune function (to fight off pathogens), triggers inflammation (to aid healing if an injury occurs), alters sex hormone (telling the body its not a good time to reproduce), impacts thyroid metabolism (speeds up metabolism), and raises blood pressure (to pump extra blood around the body)

Very high or very low cortisol levels can cause Cushings syndrome or Addison disease, both serious medical conditions, fortunately these are fairly rare


However, longterm low grade stress can also affect the body, due to cortisol levels remaining elevated and never getting the chance to return to baseline. This results in chronic HPA axis activation, causing 'cortisol resistance', where the cortisol receptors eventually become less sensitive to cortisol, similar to insulin resistance

This is when problems start to occur - over time if the HPA axis is permanently activated, it can lead to things like diabetes, autoimmune disease, heart disease, infertility, weight gain, muscle pain and depression, through the pathways described above


Fortunately there are lots of evidence backed ways you can help to 'switch off' this system, reduce stress levels and help your body recover and heal


Watch for my next post, on how to improve stress and cortisol!



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