The Role of the HPA Axis

In order to understand how adrenal issues and sex hormone imbalances manifest within the body, we need to understand how the Hypothalamus-Pituitary-Adrenal Axis functions.

The hypothalamus is a section of the brain, about the size of an almond, which has the important job of linking the nervous and endocrine systems together. The hypothalamus receives and sends inputs to and from other regions of the brain, as well as the nervous and immune systems, in order to regulate the secretion of hormones.

The hypothalamus is also is in charge of maintaining a state of homeostasis in the body. It does this by controlling many of the body’s key processes such as appetite, body temperature, heart rate, blood pressure, sleep cycles, fluid and electrolyte balance, as well as influencing the pituitary to release hormones.

The hypothalamus is in direct contact with the pituitary, a small, pea-sized, organ located at the base of the brain.  It is made up of two parts – the anterior lobe and posterior lobe.  The anterior lobe produces and releases hormones, while the posterior lobe only releases hormones. The hormones released by the pituitary regulate the functions of the other endocrine glands in the body (thyroid, adrenals, ovaries and testes).

Together the two glands form several functional axes, including the Hypothalamus Pituitary Adrenal axis, Hypothalamus Pituitary Thyroid axis and Hypothalamus Pituitary Gonad axis.

The hypothalamus could not do its job without the pituitary and the pituitary could not do its job without the hypothalamus.

The hypothalamus is directly affected by any kind of stress – real or perceived. Lack of sleep, an inflammatory diet, a virus or infection in the body, stress at work, fighting with your spouse or financial stress can all affect the hypothalamus.

When your body perceives something to be stressful, the hypothalamus releases corticotrophin-releasing hormone (CRH), which is then sent directly to the pituitary. In response, the pituitary releases adrenocorticotrophic hormone (ACTH).

ACTH is then sent directly to the adrenals, signaling to the adrenals to produce cortisol.

In a well functioning negative feed back loop the hypothalamus will sense the increased level of cortisol in the blood and slow down production of CRH.

However, this isn’t always how the feedback loop ends up working. When we are under chronic stress all of the time the hypothalamus continues to receive those signals (which tell it to continue the stress response and release more CRH), along with the signals from the already high levels of cortisol (signaling to slow down the stress response). The hypothalamus gets confused, and ends up choosing to listen to the signals telling it to produce more cortisol (because those are the life-threatening signals). This results in continued levels of high cortisol output. You can read more about what cortisol is here.

So what happens when our cortisol levels stay elevated?

There are two parts to the adrenal glands – the adrenal cortex and the adrenal medulla. The adrenal cortex is broken down into three different zones ( zona glomerulosa, zona fasciculata and zona reticularis)– all of which have different functions.

When the body is under chronic stress and the hypothalamus is continuously receiving signals to produce additional cortisol it results in more ACTH being sent from the pituitary to the zone of the adrenal cortex that produces cortisol (and less to the zones which creates sex hormones).

This can result in elevated cortisol levels (which may stay elevated for prolonged periods of time) and decreased sex hormone levels. But the issue here isn’t the adrenals – it’s the mixed signals the hypothalamus is receiving.

So as you can see, there is nothing “fatigued” about the adrenals. The adrenals are functioning just fine and doing their job of producing cortisol when signaled to do so. The issue lies with the mixed signals the hypothalamus is receiving.

So how do we get the body to stop sending mixed signals to the hypothalamus? We can start by reducing as much stress as possible – real or perceived, and making an effort to offset the stress we cannot reduce. We want to reduce the amount of time our body spends in fight or flight as much as possible. Spend more time in nature, turn off your cell phone occasionally, read and journal or do whatever alleviates stress for you.  You can read some of my favorite ways to reduce stress here.

If you suspect you may have HPA axis dysfunction, elevated (or depleted) cortisol levels or sex hormone imbalances and are interested in comprehensive hormone testing you can contact me at veronica@veronicamcnelis.com