HORMONE EFFECTS IN LYME
Updated: 17 hours ago
We wanted to share what we've learned about how Lyme and co-infections can affect our hormones (the endocrine system). So many of us notice our symptoms change with our cycles, with menopause, with stress or with thyroid problems. It isn't in our heads. This post covers how hormones and Lyme connect for both women and men, what the research and Lyme-literate doctors say, and which tests doctors may use.
Short on time or energy? A quick-view graphic with the key points is at the bottom of this post.
WHAT HORMONES DO
- Hormones are chemical messengers. They travel through the blood and tell organs in other parts of the body what to do.
- The endocrine system is the network of glands that make them. It helps run metabolism and blood sugar, the growth and work of the reproductive system, and the development of the brain and nervous system (Global Lyme Alliance, 2023).
- Two areas in the brain, the hypothalamus and the pituitary gland, act like the control center. They send signals that tell the thyroid, the adrenal glands and the ovaries or testes how much to make.
- Hormones also talk to the immune system. A Lyme-literate doctor explains that some, like cortisol, progesterone and testosterone, can calm (suppress) the immune response, while others, like DHEA, the thyroid hormone T3 and estrogen, tend to switch it on.
HOW LYME AND CO-INFECTIONS AFFECT HORMONES
- Global Lyme Alliance shares that Lyme can make its way into the endocrine system and change how our hormones work (2023).
- A Lyme-literate doctor explains that the cytokines our white blood cells make to fight Lyme can slow down the hypothalamus and pituitary. The signals they send to the thyroid, adrenals and sex organs can then be off.
- Another Lyme-literate doctor shares that Lyme and co-infections like Babesia and Bartonella raise inflammatory cytokines (IL-1, IL-6 and TNF-alpha), which can make the hypothalamus and pituitary send hormone signals irregularly.
- One Lyme-literate doctor believes infections that live in the blood vessels, like Bartonella and Babesia, can reach the brain's circulation and affect the hypothalamus and pituitary directly. This is a doctor's view.
- Dr. Horowitz's MSIDS model lists hormone problems (low adrenal function, low sex hormones and thyroid problems) as one of the effects of ongoing inflammation (2024).
- In a 2023 study of 25 people with chronic Lyme at Dr. Horowitz's practice, 20 of the 25 (80%) had low adrenal function, 7 (28%) had low thyroid function, and 6 of the 25, all men, had low testosterone. One person had no pituitary function and one had PCOS with high insulin. This was a small study of people treated at one practice.
- A Lyme-literate doctor points out that low hormones can cause the same symptoms Lyme does, such as fatigue, pain, brain fog, headaches and depression, so they are easy to miss.
ADRENALS AND CORTISOL
- The adrenal glands sit on top of the kidneys. They make cortisol, DHEA and aldosterone, which help us handle stress.
- Dr. Horowitz explains that during long or extreme stress, the adrenals go into "fight or flight" and pump out high levels of cortisol, DHEA and aldosterone. This can throw off our sleep rhythm and add to insomnia. When cortisol stays high for a long time, he says it may lead to adrenal fatigue and burnout (Global Lyme Alliance, 2023).
- Some Lyme patients have the opposite problem. Their cortisol runs low, and that can weaken the immune system (Global Lyme Alliance, 2023).
- An ILADS board doctor explains that the HPA axis (hypothalamus, pituitary and adrenals) plays a big part in our stress response. When this system gets out of balance, stress hormones can be released nonstop, which can weaken the immune response and the body's ability to fight infection (ILADEF, 2024).
- A Lyme-literate doctor explains that ongoing inflammation first pushes cortisol up. Over time cortisol drops, which can bring more fatigue and more inflammation.
- Signs of low adrenal function Lyme-literate doctors list include:
- Fatigue and an afternoon crash
- Getting sick often and recovering slowly
- Feeling shaky or irritable when hungry, which gets better after eating
- Dizziness when standing up
- Sugar cravings
- Trouble handling stress
- Insomnia with frequent waking
- Sensitivity to light, sound and chemicals
THYROID
- Dr. Horowitz shares that thyroid problems are common in his Lyme patients. Some come from adrenal problems affecting the thyroid, but many patients also have an autoimmune thyroid problem, like Hashimoto's thyroiditis (Global Lyme Alliance, 2023).
- A Lyme-literate doctor explains that inflammation can lower TSH (the brain's signal to the thyroid), slow the change of T4 into active T3, and raise reverse T3, which can block T3. Infections can also lead to thyroid antibodies.
- In a 2022 case report, doctors described a 53-year-old woman with Lyme carditis who also had painless autoimmune thyroiditis, with lab results showing an overactive thyroid. After antibiotics, her thyroid tests went back to normal. The doctors suggest considering Lyme as a possible cause of this type of thyroiditis.
- Bartonella: in a 2022 case report, a 4-year-old with cat scratch disease (Bartonella) also had autoimmune thyroiditis, which the doctors believe the infection triggered. Two months later his thyroid and thyroid antibodies were normal, and he was still well 6 years later.
- Signs of low thyroid include fatigue, weight gain, dry skin and hair, constipation, feeling cold, memory and concentration problems, low body temperature in the morning, losing the outer third of the eyebrows, puffiness around the eyes or ankles, and changes in menstrual periods (Dr. Horowitz through Global Lyme Alliance, 2023, and a Lyme-literate doctor).
- A Lyme-literate doctor notes that low thyroid and Lyme can cause such similar symptoms that they can be hard to tell apart.
WOMEN AND MEN CAN EXPERIENCE LYME DIFFERENTLY
- In a 2023 LymeDisease.org study of 2,170 people still sick 6 months or more after antibiotics (MyLymeData), women reported more co-infections, worse symptoms, a longer wait to be diagnosed, more misdiagnoses and more trouble with daily life than men. Men and women responded to antibiotics about the same, and most of both improved.
- A 2026 Johns Hopkins study of 243 adults with early Lyme found that men were more likely to test positive and to show more severe signs at diagnosis, even though both had been sick about the same length of time. Women reported more heart palpitations (11.9% vs. 4%) and vomiting (7.6% vs. under 1%), and somewhat more light sensitivity (17% vs. 8.8%, a borderline finding). Men reported more trouble sleeping (40% vs. 24.6%). Global Lyme Alliance, Bay Area Lyme Foundation and the Cohen Foundation funded this study.
- In that study, women who had been through menopause looked more like the men than like women who hadn't. The researchers plan to look at hormone levels next to learn why.
Learn more here:
DO WOMEN HAVE MORE CASES OF LYME?
SEX HORMONES AND REPRODUCTIVE HEALTH
- A Lyme-literate doctor shares that he has seen very low estrogen in young women with Lyme in his practice.
- In 2025, MIT and Fred Hutch researchers found that Lyme caused a long-lasting, severe infection in female mice's reproductive organs, with problems like an enlarged uterus, ovarian cysts and inflammation. Older mice did worse. This is animal research.
- The same team looked at patient records and survey data and found Lyme was linked with a higher risk of endometriosis (about 1.9 times the odds in one large US health records group), painful periods, heavy periods, miscarriage and uterine polyps. A Finnish database also showed more uterine fibroids, painful periods and miscarriage in women with Lyme. This early research has not been peer reviewed yet, and it shows a link, not a proven cause (MIT preprint and LymeDisease.org, 2025).
- Bay Area Lyme Foundation shared that this work by Dr. Mikki Tal at MIT is now exploring how Lyme may be tied to fibroids, endometriosis and fertility problems (2025).
MENSTRUAL CYCLES
- Global Lyme Alliance shares that Lyme symptoms often get worse during a woman's period because of changing hormones (2023).
- A Lyme-literate doctor explains that Lyme symptoms can come and go in a monthly pattern, and that this can be blamed on hormones alone when Lyme hasn't been diagnosed yet. Some women get severe PMS from the inflammation of the infection.
- In a 2024 case report from Dr. Horowitz's practice, a 21-year-old woman was feeling 100% when her night sweats, fatigue, joint pain and mood swings came back for 3 days before her period. They went away once her period started. A younger patient in the same report also flared around her cycle, and her periods added to iron deficiency anemia.
- In the 2023 Horowitz study, one woman who had been symptom-free for 2 months had symptoms come back during her cycle. The doctors felt it pointed to a low-grade infection that was still there.
- Periods can also make POTS symptoms worse:
PERIMENOPAUSE AND MENOPAUSE
- A Lyme-literate doctor shares that women who have or have had Lyme often have a harder time in menopause. Symptoms may flare as estrogen (estradiol) and progesterone drop, along with thyroid hormone, cortisol, DHEA, pregnenolone, testosterone and growth hormone.
- She adds that during this change, fatigue, brain fog, memory problems, insomnia, mood swings, headaches, joint pain, digestive issues and allergies can get worse or show up for the first time. Progesterone usually drops faster than estrogen.
- She also notes that weight gain around the middle is common in perimenopause and menopause, and Lyme can make it even harder.
- Night sweats can come from low estrogen, but sweats are also a Babesia symptom ILADS lists (2026). In a 2022 case report from Dr. Horowitz's practice, hormone testing ruled out menopause and an overactive thyroid as the cause of a woman's night sweats, and Babesia was the suspected cause.
MEN'S HORMONES
- Global Lyme Alliance shares that Lyme can lead to low testosterone in men. Dr. Horowitz notes that low testosterone can bring low energy, sluggishness, anemia, insomnia, short-term memory loss, depression and anxiety. It can also increase inflammation and weaken the immune response, which can make Lyme harder to treat (2023).
- A Lyme-literate doctor explains that in chronic Lyme, ongoing inflammation and infection disrupt the hypothalamus and pituitary, so the body makes less DHEA and testosterone. Signs of low testosterone include low sex drive, trouble keeping an erection, poor memory, irritability, low stamina, weight gain, anxiety and depression.
- Another Lyme-literate doctor shares that some of his male Lyme patients, only in their 30s and 40s, have had very low testosterone.
- In the 2023 Horowitz study, 6 of the 25 patients, all men, had low testosterone.
- MIT researchers have also found Lyme bacteria in the male reproductive tract. That work is still being studied (LymeDisease.org, 2025).
SEX DRIVE
- A Lyme-literate doctor shares that many people with Lyme lose their sex drive (libido) as part of the illness. Low DHEA and low testosterone are two of the hormone causes Lyme-literate doctors mention.
TESTS DOCTORS MAY USE
- A doctor can order labs to find out which hormones Lyme is affecting and in what way (Global Lyme Alliance, 2023).
- Adrenals: cortisol and DHEA. Some Lyme-literate doctors prefer a 4-point saliva cortisol test taken through the day. Dr. Horowitz has used a DHEA and cortisol saliva test.
- Thyroid: a full panel with TSH, free T4, free T3, reverse T3 and thyroid antibodies. A Lyme-literate doctor notes that many doctors only check TSH. Dr. Horowitz checks thyroid function along with thyroid antibodies.
- Sex hormones: estrogens, progesterone and testosterone. One Lyme-literate doctor prefers a 4-sample urine test for estrogens and progesterone, and bioavailable testosterone for men. Dr. Horowitz has also checked pregnenolone and DHEA-S.
- A Lyme-literate doctor cautions that inflammation can confuse the brain's signals, so tests like TSH can be misleading. The normal range is also wide, so you can test "normal" and still have symptoms of low hormones.
- Every Lyme-literate doctor has their own testing preferences, and that's okay.
BEFORE YOU START
- Never start, stop or change a hormone or thyroid medicine without talking with your doctor.
- Some Lyme medicines, like rifampin, can affect thyroid medicine levels, so your doctor may need to raise your dose for a while (Dr. Horowitz, 2023).
- Hormone symptoms overlap with many other conditions, so share them with your doctor instead of guessing.
MY EXPERIENCE
- When I'm fatigued, I always look into thyroid and adrenal fatigue, along with EBV and anemia.
- My Lyme-literate naturopathic doctor has me use adrenal support, rotating between two depending on my health. Adding it made a huge difference for me, and I noticed it from the very first day.
- My biggest hair loss happened once when I was anemic and once when I was hyperthyroid. Once those were fixed, my hair went back to normal.
- Our cycles affect our symptoms, and they can make POTS worse too. I once woke up 2 hours late with low blood pressure and a high pulse, feeling super weak and dizzy. That's not my normal, except during a heavy cycle.
- I had lots of hormone effects in my 30s and 40s that affected my Lyme symptoms. When menopause hit, it affected me differently. My MCAS was at its worst during menopause and after an unexpected hysterectomy.
MORE RESEARCH WITH MIXED RESULTS
- The MIT research on Lyme and gynecological problems is early and not yet peer reviewed. More research is needed.
RELATED POSTS
FATIGUE
PREGNANCY AND LYME
HAIR LOSS AND LYME
SOURCES
ILADEF, Dr. Chris Winfrey, Lyme Disease and Mental Health (2024)
ILADS, Lyme Disease Basics for Providers (2026)
Global Lyme Alliance, Lyme Disease and Hormones (2023)
LymeDisease.org, How Sex and Menopause Affect Early Lyme Symptoms (2026)
Johns Hopkins, Rebman and Aucott, Sex and Menopause in Early Lyme Disease (2026)
LymeDisease.org, Gender Disparities in Lyme Disease (2023)
LymeDisease.org, Lyme Disease and Gynecological Health Risks (2025)
MIT and others, Lyme disease and gynecological conditions, medRxiv preprint (2025)
Bay Area Lyme Foundation, Dr. Mikki Tal on Fertility and Immunity (2025)
Dr. Richard Horowitz and Phyllis Freeman, 25-Patient Study, Microorganisms (2023)
Dr. Richard Horowitz and Phyllis Freeman, 3 Case Reports, Microorganisms (2024)
Dr. Richard Horowitz and Phyllis Freeman, Case Reports, Antibiotics (2022)
Lyme Thyroiditis and Carditis Case Report, AACE Clinical Case Reports (2022)
Bartonella Autoimmune Thyroiditis Case Report, Pathobiology (2022)
Dr. Todd Maderis, Hormones in Lyme Disease (2022, updated 2023)
Dr. Marty Ross, Thyroid and Adrenals in Lyme and Low Sex Drive in Lyme (updated 2026)
Dr. Susan Marra, Menopause and Lyme Disease, and Andropause (no date shown)
Disclaimer: Rise Above Lyme makes no claims about any possible benefit of using any product mentioned within this site. Always consult with your doctor before adding anything. The information shared is based on personal experience, years of accumulated researched resources from Lyme Literate doctors and polls conducted within Lyme groups from actual patient experience using these solution ideas.
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