The HPA Axis Part 2: The Four Types of Hormones
In part 1, we covered what the HPA axis is and how the hypothalamus, pituitary, and adrenal glands work together in this axis to produce a variety of hormones necessary for our health. Today, we are going to dive into the four categories of these hormones, all of which are found and made in the adrenals.
As we discussed, the adrenals have two sections, the medulla and cortex.
The medulla is the simplest - it has only one layer and produces catecholamine hormones otherwise known as epinephrine and norepinephrine (adrenaline and noradrenaline as they are also known). These are our "fight or flight" hormones and are released when we sense any threat. They increase blood pressure and blood flow to prepare our body to "fight." They work with cortisol in this aspect, but rise more quickly than cortisol in response to acute stressors.
The cortex has three layers, each of which produce a different set of hormones,
The zona reticularis in the cortex produces anabolic hormones like DHEA, pregnenolone, progesterone, estrogen, and testosterone. Anabolic means to "build up" and these hormones are produced to help build up our body's hormone reserves as the sex glands produce the larger amount of most of these hormones. This is especially important in women who go through menopause, as they start to use these hormones when the ovaries become unresponsive to FSH (follicle stimulating hormone).
The simple version of all that? We need those hormone reserves to be just that - reserves so that when the time comes, we can use them. If we are constantly calling upon them before they are supposed to be used because stress/dysfunction elsewhere in the body has depleted our true sex hormone stores, we will not have any reserves to use when the time comes.
The zona fasiculata in the cortex of the adrenals produces glucocoritcoids, which includes hormones like cortisol, and influence protein, fat, and carbohydrate metabolism; blood sugar regulation; and are meant to be anti-inflammatory in the right amounts. We need cortisol, our stress hormone, to survive, but too much of it long term starts to cause severe problems. We will discuss this in part 4.
Lastly, the zona glomerulosa in the cortex produces mineralocorticoids. These are hormones that regulate fluids, inflammation, and sodium in the body, the most common being aldosterone.
Whew - that's a lot of hormones and fancy words! Just know this - these hormones, even if they seem overwhelming, are what work to keep our body in homeostasis. We will be discussing what can harm this homeostasis in the next post. Stay tuned!