The Brain, the Endocrine System, and the Gut Microbiome: How They Work Together
In order to support our daily habits and seasons of life, our bodies, specifically bodily systems, need to be in constant communication with one another to find balance in the ebbs and flows. The endocrine system, a bodily system involving glands and organs that coordinate the body’s metabolism, energy level, reproduction, and more, uses vital communication pathways to help other parts of the body facilitate their roles.
This type of communication, or more specifically, feedback loops, involves the HPA axis, HPO axis, and HPT axis. Each axis shares the same command centers in the brain: the hypothalamus and pituitary gland.
HPA: Hypothalamus-pituitary-adrenal
HPO: Hypothalamus-pituitary-ovarian
HPT: Hypothalamus-pituitary-thyroid
Let’s dive in to see how these endocrine-related axes function on their own as well as how they impact each other.
HPA, HPO, HPT
HPA: Hypothalamus-Pituitary-Adrenal
The HPA axis involves three organs: hypothalamus, pituitary gland, and adrenal glands (located above your kidneys). They work together to maintain hormonal balance and respond to stress, as the main function of the HPA axis is to release cortisol. In going beyond stress management, the HPA axis also plays a crucial role in mood, digestion, immune function, and energy in the body.
HPO: Hypothalamus-Pituitary-Ovarian
When it comes to fertility or menstruation, you may not think about how the brain could play a role. With the HPO axis, we’re able to see how two areas in the brain communicate directly to reproductive areas, such as the ovaries. The hypothalamus and pituitary gland release hormones FSH (follicle-stimulating hormone) and LH (luteinizing hormone) and if the HPO is not functioning fully, it can lead to irregular menstrual cycles, development issues, and fertility.
HPT: Hypothalamus-Pituitary-Thyroid
As the brain receives external stimuli like light exposure, it begins to release hormones like TSH, or thyroid-stimulating hormone. TSH then signals to the thyroid to produce T3 and T4, which are involved in controlling metabolism.
How Each Axis Is Related
As each axis shares the hypothalamus and pituitary organs, these lines of feedback communication loops can become disrupted if one becomes overactive or suppressed.
As the HPA axis involves stress management and reacting to stress, it can lead to an imbalance of estrogen and progesterone (affecting HPO), as well as reducing the amount of TSH released (affecting HPT). In another example, if there isn’t enough thyroid hormone being released, it can prevent or interfere with ovulation, or the release of an egg. Cortisol can also block the formation of thyroid hormones, leading to hypothyroidism.
Gut Health
The gut microbiome, the brain, and the endocrine system have a complex relationship but are deeply entwined. Below are ways all three affect one another:
Using hormones like cortisol, the gut and brain have bidirectional communication using the vagus nerve.
The bacteria in our gut help process hormones like estrogen for hormonal balance, as well as processing nutrients that fuel hormone production. Gut dysbiosis can lead to estrogen dominance, which has been associated with PCOS and other estrogen-related conditions and symptoms.
A disrupted gut microbiome can contribute to autoimmune diseases that affect the thyroid.
Short-chain fatty acids (SCFAs) produced in the gut have anti-inflammatory properties, which affect hormone regulation.
Maintaining a healthy gut has a cascade effect on many systems that may seem unrelated. These examples are reasons why I take a whole-body approach to health. As my clients come to me with hormone imbalances, gut dysbiosis, or feeling lost in their health journey, I take a step back to evaluate the systems at play to get to the root cause of the issue.
If you’re interested in learning more, check out my Hormone Health Intensive, Gut Health Intensive, and 3-or-6-Month Optimal Health Programs to learn more!