The hypothalamus-pituitary-adrenal (HPA) axis
by Ian Craig
in Blogs

The HPA axis used to be a bit of a well kept secret to nutrition and functional practitioners - it helped them to understand what was happening to the endocrine (hormonal) system of a stressed out client who was devoid of energy and was potentially struggling with their weight. Now the term ‘HPA axis’ has come into more common use in health language, but I’ll bet that the majority of you don’t actually know what it means, or at least what is significant about it!

Since I explain this concept to one or more clients almost every day, I thought that it would a useful blog resource for you, so listen carefully and I’ll share my lay person explanation with you…

The hypothalamus is considered the master gland in our body, which orchestrates our endocrine system by sending signals to the pituitary gland, which in turn sends releasing factors to the relevant glands. The hypothalamus and pituitary (the HP-axis) also seamlessly interact with our nervous system, so it makes sense that when we’re stressed, both our hormones and nerves react in the same stressed way.

The endocrine system is obviously a lot more complex than this, but the first diagram below gives a good representation of how the HP-axis inter-relates with three incredibly important glands - our gonads (ovaries in women and testes in men), adrenal glands, and thyroid gland:

  • - Gonads - secrete sex hormones, and are involved in sexual and reproductive functions
    - Adrenals - secrete stress hormones (adrenaline and cortisol) for energy and general function, plus provide some blood pressure support
    - Thyroid - secretes thyroxine, considered important for our energy and metabolism

HPA 1 copy

In an ideal world, our hypothalamus and pituitary glands would orchestrate these glandular functions fluently, allowing; good sexual energy, a consistent monthly cycle in women, healthy conception and birth of healthy babies, sustained energy levels when needed, a vibrant metabolism, and a healthy body composition.

Our hormones probably worked like that when we were still cavemen and cavewomen, assuming we weren’t going through a period of famine. However, modern life throws in its own challenges and typically this balanced hormone scenario starts to deviate from perfection at some point in a person’s 30’s, although it often happens much earlier than that.

Dipping back to the olden days for a moment, our adrenal (stress) glands would always take priority over our reproductive organs and our metabolism - you can imagine the scenario of a wild beast charging towards you, and then turning to your wife and saying; “do you fancy a quickie before we get eaten?!” No, we would active our fight and flight system (HPA axis) as strongly as possible and try to run away or fight - sex can come later if we survived.

It’s the same in modern life - even though the stresses are mostly not life threatening, our adrenal system always takes priority. So, if you look at the next diagram below, you’ll see that the arrow to the adrenal glands has been super-sized and the arrows to our gonads and thyroid gland have been crossed (to mean inhibited). To give you another scenario; imagine in a family setting that the hypothalamus and pituitary glands represent mum and dad, and that the adrenal, thyroid and gonads are three children. What happens when we have one naughty child in the family who requires a lot of attention? The other two might become neglected, meaning that our thyroid gland and gonads do not receive sufficient support from our hypothalamus-pituitary axis. They then under-function or become imbalanced, while the adrenal glands are driven so strongly that they eventually burn out.

In theory, this hormonal system has a negative feedback system (denoted by the curvy arrow in the diagram). This means that if any particular gland is being pushed too hard, it will send a message to the hypothalamus to say “slow down” or “stop bullying me”! In reality, we have an extremely powerful organ that sits all around the HP axis and that is called the brain. The brain is conditioned by two parts of our mind: firstly our conscious mind pushes us to get up in the morning, to take the kids to school, to meet work or study deadlines, and to achieve a certain amount of exercise, which might be hard stuff like CrossFit if we are generally tough on ourselves. Additionally, we have the unconscious mind that may have been conditioned to be a hard worker by watching our parents as we grew up, and by certain societal or cultural expectations. All in all, the subtle feedback loops of our glands are often ignored in our moderns lives, meaning that we keep pushing our poor hormones.

HPA 2

Before burning out our glands, excessive levels of adrenaline and cortisol over time can deplete our immune response, destabilise our blood sugar levels, make us tense and anxious, increase inflammation and auto-immune tendencies, deplete muscle and bone mass, and ironically in many cases, increase body fat.

So you can see why us practitioners give so much attention to the HPA axis - all of us need to work hard to decrease the stress response in our lives and we can do this by engaging in relaxing/recuperative activities, which may include mediation, yoga and Tai Chi, but could also involve walking in nature, being with like minded people, spending time with animals, and taking up mindful hobbies such as music and art. Anything really that lifts us up by the scruff of the neck, off the whirling treadmill of life, even just for a few moments every day.

Take a minute to think about which activities in your life might help bring some balance to your HPA axis.