Immune System Hormone Guide: How Your Hormone Health Affects Your Immune System

Dr. Jolene BrightenPublished: Last Reviewed: Balancing Your Hormones Leave a Comment

Your immune system is your body’s natural defense system, protecting your health against disease and infections. It’s a tough job, and with everything in the news, most of us are eager to boost our immunity however we can. A quick search will reveal hundreds of tips to eat right, exercise more, and sleep better to get your immune system working top notch. But one often overlooked key to immune system health is your hormonal health.

Balanced hormones are a major key to healthy immunity, and a weak immune system could even be a sign of a hormonal imbalance. Let’s jump in to discuss the connection between hormones and the immune system.

Which Hormones Are Responsible for the Immune System?

While we often talk about them separately, your immune system and your endocrine system work hand in hand to maintain your health. Your individual hormones also impact each other, which is part of the reason why identifying hormone imbalances can be so impactful for your health.

Estrogen, serotonin, cortisol and more all influence your immune system, and can have a direct effect on keeping you flu-free. Hormones can also play a part in an immune system that overreacts. Autoimmune conditions, which sometimes relate to hormone imbalances, occur when your immune system goes to work overtime, mistakenly attacking your own cells. 

For women and menstruating people specifically, the effects of  sex hormones on the immune system pack some super unique benefits and risks! 

According to a peer-reviewed paper published in 2018, “Women mount stronger immune responses against foreign but also against self-antigens, and the prevalence of most autoimmune diseases (AD) is greatly increased in women compared to men.”

In other words, estrogen’s role in the immune system can help to explain why women generally have stronger immune systems than men, but also a higher prevalence of autoimmune disease. 

Let’s take a look at six key hormones to unpack their impact on our immune health. 


Estrogen helps enhance the inflammatory response of your immune system, your body’s natural method for mounting an attack against an invading threat. 

Research shows that a woman’s immune system is generally at its strongest during her reproductive years—when estrogen is at its highest. As women age, lower estrogen levels during and after menopause are associated with reductions in immune function.

Generally, estrogen boosts the immune system, while testosterone can inhibit it, which could partly explain why women tend to have stronger immune responses than men (and higher rates of autoimmunity). 

Estrogen receptors appear in tissues all over your body. Within the immune system, estrogen boosts B cell and T cell function, two key players in fighting off pathogens. Estrogen also helps support heart health, reducing the risk of heart disease by promoting healthy blood flow, and helping the immune system defend against infections linked to atherosclerosis. 

However, it is possible for estrogen to boost your immune system too far. This is one of the risks of estrogen dominance, the most common hormone imbalance I see in women. With excess estrogen enhancing the immune process, the body can turn to an autoimmune response, where your immune system mistakenly attacks your own cells.  

For women with autoimmune conditions, peaks and dips in estrogen can cause flares or changes in autoimmune symptoms, especially throughout the hormonal roller coaster of perimenopause.

If you’re dealing with hormone imbalances that could be leading to other symptoms, my free Hormone Starter Kit is designed especially for you.


While we usually think of progesterone as a sex hormone, progesterone receptors are also found all across the body, including immune cells such as macrophages, T cells, killer cells, and B cells, as well as protective cells like epithelial, endothelial, and mucous membrane cells. This means progesterone impacts a lot more than just fertility.

In general, progesterone and estrogen tend to have opposite effects in the body, each balancing the other's effects to maintain a healthy equilibrium. While estrogen boosts the immune response by promoting inflammation, progesterone triggers immune cells to reduce inflammation. Progesterone cools the inflammatory response, activates anti-inflammatory T-cells, and tells your mucosal cells to focus on repair. 

When progesterone dips too low, your body can experience a relative estrogen dominance, pushing your immune system into overdrive, a.k.a. autoimmune territory. Maintaining a healthy balance between estrogen and progesterone production is crucial for keeping your immunity in its goldilocks range — not too weak and not too strong. 


Most of us know cortisol as the stress hormone, and boy can I tell you: when stress goes up, health goes down. It’s not just anecdotal, either: studies have linked psychological stress to a greater susceptibility for infectious diseases. So — what happens when your immune system gets too stressed out?

In a balanced, healthy immune system, cortisol actually has an anti-inflammatory effect. Cortisol activates the body’s sympathetic nervous system, known as your “fight-or-flight” response. Basically, when our hunter-gatherer ancestors were fleeing a predator, they wanted all their energy focused on one thing: running really, really fast. A burst of cortisol is meant to help our bodies prioritize energy for instant survival in high stress situations, saving tasks like immune defense, inflammation or digestion for after the threat has passed.

But when stress shifts from short “fight-or-flight” bursts, to chronic stress, elevated cortisol does more harm than good. Among the myriad of ways chronic stress wreaks havoc on your health, chronically high cortisol levels can lead to immune cells ignoring cortisol signaling. As your immune system becomes resistant to cortisol’s anti-inflammatory signals, inflammation levels rise unchecked. High stress leads to high inflammation, the perfect recipe for autoimmune conditions, immune dysfunction, and other illnesses.

To make things worse, chronic stress also depletes serotonin, and causes your body to preferentially produce cortisol instead of progesterone. Without progesterone to balance it out, this throws your body into a state of relative estrogen dominance, further driving up inflammation.

While stressful situations may be unavoidable, it is possible to reduce your own stress and thereby prevent the effects of chronic high cortisol on your body. Lifestyle shifts like meditation and gratitude, or natural supplements like L-Theanine are great places to start.


If all that talk about stress made you want to go hug your cat — good! Let’s talk about oxytocin next, fondly dubbed the “cuddle hormone.” The hypothalamus produces oxytocin in response to affectionate physical touch, be that kissing, hugging, or holding hands with a loved one, or even snuggling up with your pet. 

On top of giving us the “warm fuzzies” and fighting anxiety and stress, oxytocin lowers cortisol levels, helping to undo some of the negative effects of chronic stress on your immune function. Multiple studies show that oxytocin receptors also play a part in lowering chronic inflammation, promoting wound healing, increasing immune defenses, and even enhancing the function of antibiotics.

Want to know another great way to boost oxytocin? Orgasms. Yep, good sex can actually help your immune system. Win-win.


Serotonin (also known as 5-hydroxytryptamine, or 5-HT) is both a neurotransmitter and a hormone. You may know it as the “happy molecule” because of its role in the brain regulating happiness, anxiety, and mood. A serotonin deficiency is best recognized through depression and anxiety, but can also affect your digestion, sleep, inflammation, and immune system.

Serotonin affects your immune and inflammatory responses by activating a whole range of cells with serotonin receptors throughout your immune system. Some immune cells, such as mast cells, T lymphocytes and some macrophages can actually produce serotonin themselves to further the immune response. Depending on the cell, serotonin activation can increase production of cytokines, chemokines, and lymphocytes — and recruit immune cells to join the fight where they are most needed. 

Increasing your serotonin levels can support your mood and immune system and help regulate healthy digestion, sleep, bones, inflammation, libido, and memory. It's possible to boost serotonin activity naturally, or through supplements or medications.


Prolactin is a hormone secreted at its highest during and after pregnancy. It’s best known for preparing a woman’s body for breastfeeding and producing milk. Outside of pregnancy, it has a pro-inflammatory effect (meaning it actually increases inflammation) and helps modulate several immune cell responses.

One of prolactin’s most important immune roles during pregnancy is helping the immune system shift from a state of Th1 dominance, to its more subdued state of Th2 dominance. We’ll talk more about that below, but this shift is crucial in allowing your immune system to accept sperm and a fetus instead of seeing them as outside invaders.

Does the Immune System Weaken While Pregnant?

Yes, in order to have a successful pregnancy, a woman’s immune system is actually slightly weaker during certain parts of pregnancy. 

Generally speaking, your immune system’s job is to fight off anything it deems “not you,” like viruses, bacteria, or other threats. This means pregnancy — accepting and protecting a “not you” baby — requires a huge readjustment for your immune system. Add to that a chaotic scrambling of every hormone your immune system relies on, and your body’s in for some serious changes during and after carrying a baby. 

In order to sustain a healthy pregnancy and conception, women who are pregnant or fertile experience a shift in their immune system from its more aggressive Th1 state, to a more tolerant Th2 state.

This means that the immune system is actually less aggressive during pregnancy. While that might sound concerning, a woman’s body is actually designed for this shift! Remember that a woman’s immune system is naturally on the high side to begin with, so this downregulation is usually not a concern. In fact, this dialing down of the immune response could also explain why some women experience a relief from autoimmune symptoms during their pregnancy.

Does Hormone Therapy Weaken the Immune System?

Some research suggests that hormone replacement therapy (HRT) in postmenopausal women may actually boost your immune system. As we age, our immune systems (among other things) tend to start drooping. The drastic drop in sex hormones accompanying menopause definitely plays a role.

HRT is somewhat controversial medically because evidence is mixed, with some studies showing an improvement in atherosclerosis and cardiovascular disease, but other research suggesting no effect or the opposite effect. (My opinion? Some of the larger studies didn’t use proper HRT protocols, and HRT isn’t for all women anyway — I’m in favor of it in some cases, but not for every single woman.)

Other research suggests that HRT can help reverse some of the aging effects of menopause on the immune system. In this study, postmenopausal women using Estrogen-Progestin HRT saw more B-cells, more responsive T-cells, and higher TNF-alpha levels, all indicators of a stronger immune response.

That said, hormone replacement therapy is a serious choice that impacts way more than your immune system. If you’re considering HRT to offset the effects of menopause, talk with your doctor about side effects, synthetic vs. bio-identical hormones, and other treatment options.

The Importance of Balancing Hormones for Immune Health and More

I hope this article helps shed some light on the importance of balancing hormones for improved immunity. A reduced immune system is just one symptom that something’s up; a hormone imbalance can also cause changes to your mood, energy, weight, skin, periods, sleep and more!! Fortunately, there are many natural ways to balance hormones, and understanding your body’s signals is step number one. Hormone supportive foods, healthy fats, and knowing how and when to use supplements can help dial in a healthy hormone balance, and keep your immune system living its best life.

To start, download your FREE Hormone Starter Kit with 7 Day Meal Plan & Recipe Guide Book.

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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.