One man’s bones proved estrogen matters for men as well as women

Key takeaways

• In 1994, doctors described a 28-year-old man who was still growing at about 6 feet 8 inches and had thin bones, because his body couldn’t respond to estrogen.
• In a 2013 trial of about 400 healthy men, blocking estrogen raised body fat at every testosterone dose tested, and it made sexual function worse.
• A 2021 analysis of 41 clinical studies found that soy protein and soy isoflavones did not change men’s testosterone or estrogen levels.
• The FDA-approved label for one birth control pill estimates 3 to 9 clots a year per 10,000 users, compared with 1 to 5 among women who aren’t pregnant and don’t use the pill.
• “Estrogen dominance” is an informal label some health care providers use when estrogen acts without enough progesterone to balance it, so ask which condition and which test a clinician has in mind.

In 1994, a medical team reported on a tall young man in the New England Journal of Medicine¹. He was 28 years old and about 6 feet 8 inches tall, and he was still growing¹.

The growth plates at the ends of his long bones had never fully closed¹. His spine bones were thin, far below the average for young women his age¹. Otherwise, he had gone through a normal male puberty¹.

The puzzle was his blood work. His estrogen levels were high, and his testosterone was normal¹. When doctors gave him estrogen through the skin for six months, his free estradiol rose about tenfold, yet his body showed no response¹.

The cause was genetic. Both copies of his estrogen receptor gene carried a mutation, so his cells couldn’t “hear” the hormone¹. The authors concluded that estrogen matters for bone growth and mineral strength in men as well as women¹.

That one patient upends a common idea. Estrogen gets called “the female hormone,” but it works throughout the body in everyone. Below, we look at what it does, what soy and birth control mean for it, and how to read popular claims about it.

Three estrogens, more than one factory

“Estrogen” is a family name. The Endocrine Society, a professional group of hormone specialists, describes three main members².

• Estradiol is the strongest and the most common type during the childbearing years².
• Estrone is weaker. Women tend to have more of it after menopause, and it comes from the ovaries, fat tissue and adrenal glands².
• Estriol is the third member of the family².

The ovaries make most of a woman’s estrogen before menopause. Fat tissue and the adrenal glands add small amounts². When a woman’s estrogen falls, the usual reason is menopause or an operation that took out her ovaries².

Men make estrogen too, and they need it in lower amounts than women². Testosterone is one source. An enzyme called aromatase converts testosterone into estrogen, and drugs called aromatase inhibitors block that step³.

Body size matters here. Women with obesity make more estrone from their fat tissue², one real way estrogen exposure can run high.

What estrogen does, from bones to brain

Estrogen works by attaching to receptors, proteins in cells that respond to it. The 1994 patient shows what happens when they fail¹. This table, our own summary, shows estrogen’s main jobs and what can happen when levels run low.

Body part	Estrogen’s job	When levels are low	Source
Bones	Helps bones mature and harden, in men as well as women	Slower bone growth; over time, osteoporosis	12
Ovaries and uterus	Estradiol triggers egg release and thickens the uterine lining	Fewer periods or none	2
Vagina	Keeps tissue moist and thick	Dryness and thinning	2
Body fat	Helps regulate how much fat builds up	In men, extra belly fat	23
Brain and mood	Supports brain function in men; tied to mood in women	Mood swings, hot flashes, night sweats, sleep trouble	2
Skin	Helps keep skin from drying out	Dry skin	2
Sexual function	Plays a part in desire in women and men	Low sex drive	23

More is not better. Very high estradiol in women may raise the risk of uterine cancer, breast cancer and heart disease, the Endocrine Society notes². In men, too much estrogen can cause enlarged breasts, poor erections and infertility².

Men run on estrogen, too

The 1994 case was one man with an unusual mutation. A later experiment asked what estrogen does in ordinary men.

In a study published in 2013, researchers at Massachusetts General Hospital recruited healthy men aged 20 to 50³. First, a drug shut down each man’s own sex hormones³⁴. For the next 16 weeks, the men got a placebo gel or testosterone gel at one of four doses, chosen by chance³.

The twist was a second group of about 200 men. They got the same setup plus anastrozole, an aromatase inhibitor that kept testosterone from becoming estrogen⁴.

The results split the work between the two hormones. Muscle size and leg strength fell only when testosterone got quite low, and blocking estrogen didn’t change them³. Body fat was different: with estrogen blocked, fat rose at every testosterone dose³.

Sexual function needed both hormones. Desire fell as testosterone fell, and blocking estrogen made sexual function worse at every testosterone level³⁴. The lead researcher, Joel Finkelstein, said falling estrogen may explain part of what gets blamed on low testosterone³.

Two caveats matter. The hormone drop was created on purpose in men aged 20 to 50, and the team planned follow-up studies in older men³. And industry helped: Solvay Pharmaceuticals, now part of Abbott, funded the study, Abbott supplied the testosterone gel, and AstraZeneca supplied the hormone-blocking drugs⁴.

Testosterone, and supplements sold to raise it, get their own articles in this series.

Soy and plant estrogens: what human studies show

Soybeans contain isoflavones, plant compounds shaped much like human estrogen⁵. That resemblance fuels two common worries: that soy feminizes men, and that it feeds breast cancer.

Men’s hormones. In 2021, researchers pooled 41 clinical studies in the journal Reproductive Toxicology⁶. Testosterone was measured in 1,753 men and estradiol in 1,000⁶. Neither soy protein nor isoflavones changed testosterone, free testosterone, estradiol or estrone, whatever the dose or study length⁶.

A note on funding: one author, Mark Messina, is listed with Nutrition Matters, Inc., a private company⁶. The records we reviewed showed no funding statement, so weigh the analysis with that in mind.

Breast cancer. The National Center for Complementary and Integrative Health (NCCIH), part of NIH, reports that Asian and Asian American women who eat more soy have a lower breast cancer risk in observational studies⁵. Those studies watch what people eat rather than assigning it, so they show a link, not proof. NCCIH adds that typical Western diets may hold too little soy for the pattern to show⁵.

Pills are a different story. Soy supplements haven’t been shown to lower breast cancer risk⁵. If you’ve had breast cancer, our article on beans and legumes covers what cancer researchers say about soy foods for survivors.

Hot flashes. Soy protein or isoflavone supplements may cut hot flashes a little, but results haven’t been consistent⁵.

Safety. NCCIH reports that soy protein supplements have been used safely for up to 16 weeks and isoflavone extracts for up to 6 months⁵. Side effects include bloating, constipation, diarrhea and nausea⁵.

Two cautions apply. Tofu and soy sauce can be high in tyramine, which may interact with MAOI antidepressants and push blood pressure dangerously high⁵. And in pregnancy, soy in amounts beyond normal food may be unsafe⁵.

The pill’s clot risk is real, and small in absolute terms

Combined hormonal birth control pairs an estrogen with a progestin, as in the pill whose label we cite here⁷. The CDC’s eligibility tables group combined pills, patches and rings together¹⁰. These methods can raise the risk of venous thromboembolism, a blood clot in a vein, such as in the legs or lungs⁷.

How the FDA-approved label for one combined pill puts it⁷:

Group	Clots per 10,000 women per year
Not pregnant, not using the pill	1 to 57
Using a combined pill	3 to 97
Pregnant or recently gave birth	About 20, by our math8

Our pregnancy figure converts a rate of 0.2 per 100 years at risk from a 2011 commentary in the Canadian Medical Association Journal (CMAJ)⁸. The label gives no pregnancy number but says the rate runs even higher than on the pill, especially after birth⁷.

By our math, the pill adds roughly 2 to 4 clots per 10,000 users a year, about 1 extra case for every 2,500 to 5,000 women.

Relative numbers sound scarier. The same CMAJ commentary described combined pills as raising clot risk three- to fivefold, while stressing that the absolute risk in young women is low⁸. Estimates differ between studies, and by our math, the label’s own ranges imply a smaller jump.

Timing matters, and the type of progestin may too. The risk is highest in the first year, especially soon after starting a pill or restarting after a break of four weeks or more⁷. Studies comparing pills containing the progestin drospirenone with other pills ranged from no difference to a threefold increase⁷.

Who shouldn’t use estrogen. The pill’s boxed warning, the FDA’s most prominent kind, says smoking raises the risk of serious heart and blood vessel events, and that women over 35 who smoke shouldn’t use it⁷.

The CDC’s 2024 U.S. Medical Eligibility Criteria sort health conditions into four categories, from 1 (no restriction) to 4 (unacceptable health risk)⁹. Conditions in category 4 for estrogen-containing methods include¹⁰:

• age 35 or older and smoking 15 or more cigarettes a day;
• the first 21 days after giving birth;
• a past clot in a deep vein or lung with a higher chance of recurrence, or a known inherited clotting disorder;
• a top blood pressure number of 160 or higher, or a bottom number of 100 or higher;
• ischemic heart disease (narrowed heart arteries), stroke or complicated heart valve disease;
• migraine with aura;
• current breast cancer;
• lupus with positive or unknown antiphospholipid antibodies;
• severe liver disease or certain liver tumors.

One surprise: obesity alone is category 2 for estrogen-containing methods, meaning the benefits generally outweigh the risks⁹¹⁰. These are tools for your prescriber. If something on this list applies to you, raise it at your next visit rather than stopping your birth control on your own.

“Estrogen dominance” is a loose label for a real concern

You may have heard the phrase “estrogen dominance.” Pages that use it tie it to fatigue, weight gain, mood swings, low sex drive and tender breasts¹¹.

Cleveland Clinic, an academic medical center, explains where the phrase comes from. When the body makes too much estrogen, or too little progesterone to offset it, doctors call the result “unopposed estrogen,” and some providers call it “estrogen dominance”¹¹. Unopposed estrogen acting on the uterus is a common risk factor for endometrial hyperplasia, an overgrowth of the uterine lining¹².

So there’s a real concern buried in the phrase. The trouble is everything wrapped around it. The symptom list is broad, and complaints like tiredness and weight gain have many possible causes¹¹.

Testing is tricky, too. In people who still have periods, Cleveland Clinic notes, estrogen rises and falls through the month, so a blood result may not be accurate¹¹.

What the sources tie to high estrogen:

• Excess body fat. Women with obesity make more estrone from fat tissue, and excess estrone has been linked to the growth of breast and endometrial cancers².
• Hormone medicines. Menopause hormone therapy can push levels too high at first, and a combined birth control pill can also supply too much¹¹.
• Linked conditions. Cleveland Clinic lists some cancers, plus tumors of the ovaries and adrenal glands, among complications tied to high estrogen, while noting that estrogen doesn’t necessarily cause them¹¹.

Environmental chemicals that act like estrogen are covered in two companion articles, What scientists mean by endocrine disruptor and what labels mean and Why the FDA and Europe disagree about BPA.

If someone tells you that you have estrogen dominance, ask three questions. Which medical condition do you suspect? Which test would confirm it, and when in my cycle should it be drawn? What would we do differently based on the result?

Our article on “balance your hormones” claims explains why saliva tests aren’t a reliable way to answer them.

Estrogen myths and facts

Here’s our rating of common claims, using the library’s four-level evidence scale.

Claim	What the evidence shows	Rating
Estrogen is only a women’s hormone	Men need it for bone growth and fat regulation, and it affects their sexual function123	Evidence says no, or unsafe
Soy leaves men’s testosterone and estrogen unchanged	41 clinical studies found no change, at any dose or study length6	Strong evidence
Soy foods lower breast cancer risk	Seen in Asian and Asian American women in observational studies, which can’t prove cause5	Promising but early
Soy supplements prevent breast cancer	Not shown to lower risk5	Not enough evidence
Soy or isoflavone pills ease hot flashes	Small, inconsistent benefit5	Promising but early
Combined birth control raises clot risk	Real, highest in year one, small in absolute terms78	Strong evidence
Body fat makes estrogen	Fat tissue makes estrone, more so with obesity2	Strong evidence
“Estrogen dominance” can be diagnosed from a symptom list	Informal label; symptoms are broad and blood levels swing11	Not enough evidence

Where natural health and hormone science meet

Many natural-health traditions trust the body’s own systems. The estrogen story rewards that trust. Your body makes estrogen in several places, converts one hormone into another as needed, and adjusts across the month and the lifespan²³.

It also supports a food-first instinct. Soy foods such as tofu and edamame have a reassuring research record, while concentrated soy pills have less to show⁵⁶.

Prevention fits here, too. Body fat is an active hormone source². By extension, habits that affect weight can affect estrogen exposure. And for anyone using estrogen-containing birth control, not smoking matters, because smoking drives the pill’s most serious risks⁷.

The history of estrogen as a medicine is a story of its own. Our article on observational studies explains how the Women’s Health Initiative changed thinking about hormone therapy, and our menopause sleep article covers recent changes to hormone therapy labels. Decisions about menopause hormone therapy get their own article later in this series.

Questions readers ask

The bottom line

Estrogen is a whole-body hormone for everyone. It helps growth plates close, hardens bone, helps regulate body fat and helps drive sexual function in men and women alike. Rare genetic cases and careful experiments show what goes wrong without it.

Soy foods don’t appear to scramble anyone’s hormones. The pill’s clot risk is real but small in absolute terms, and lower than pregnancy’s. “Estrogen dominance” points at a real concern, unopposed estrogen, but wraps it in vague symptoms. When hormones are in question, ask for the named condition and the right test.

Related reading

• Real hormone problems have names and tests, which “balance your hormones” claims lack
• Why observational studies got smoking right and hormone therapy wrong
• Hot flashes aren’t the only thing stealing sleep in menopause
• Cooked beans are cheap and well studied, and the lectin scare applies to raw ones
• A progesterone-like shot failed its big test, and progesterone still helps in a few places

Sources

1. Smith EP, Boyd J, Frank GR, Takahashi H, et al. “Estrogen Resistance Caused by a Mutation in the Estrogen-Receptor Gene in a Man.” New England Journal of Medicine, 1994 (abstract via Read by QxMD; author record via JCI Insight). qxmd.com and pubmed.ncbi.nlm.nih.gov
2. Endocrine Society. “Reproductive Hormones.” Endocrine Library, updated January 24, 2022. endocrine.org
3. Massachusetts General Hospital. News release on Finkelstein JS, et al., “Gonadal Steroids and Body Composition, Strength, and Sexual Function in Men,” New England Journal of Medicine, 2013. ScienceDaily, September 2013. sciencedaily.com
4. Urology Times. “Low Estrogen Levels May Play Role in Hypogonadism” (on NEJM 2013;369:1011–22). 2013. urologytimes.com
5. National Center for Complementary and Integrative Health. “Soy: Usefulness and Safety.” NIH, updated April 2025. nccih.nih.gov
6. Reed KE, Camargo J, Hamilton-Reeves J, Kurzer M, Messina M. “Neither Soy Nor Isoflavone Intake Affects Male Reproductive Hormones: An Expanded and Updated Meta-Analysis of Clinical Studies.” Reproductive Toxicology, 2021;100:60–67 (University of Essex repository record). repository.essex.ac.uk
7. U.S. Food and Drug Administration. YAZ (drospirenone and ethinyl estradiol) tablets: Prescribing Information and Patient Information, revised May 2023. accessdata.fda.gov
8. Canadian Medical Association Journal. Commentary on Gronich N, Lavi I, Rennert G, “Higher Risk of Venous Thrombosis Associated With Drospirenone-Containing Oral Contraceptives.” CMAJ, 2011;183(18):E1278. cmaj.ca
9. Centers for Disease Control and Prevention. “U.S. Medical Eligibility Criteria for Contraceptive Use, 2024.” MMWR Recommendations and Reports, 2024;73(4). cdc.gov
10. Centers for Disease Control and Prevention. “Appendix K: Summary of Classifications for Hormonal Contraceptive Methods and Intrauterine Devices.” U.S. MEC 2024, updated November 19, 2024. cdc.gov
11. Cleveland Clinic. “High Estrogen: Causes, Symptoms, Dominance and Treatment.” Updated April 17, 2026. my.clevelandclinic.org
12. Cable JK, Grider MH. “Physiology, Progesterone.” StatPearls, NCBI Bookshelf, National Library of Medicine, updated May 1, 2023. ncbi.nlm.nih.gov
13. Centers for Disease Control and Prevention. “Signs and Symptoms of Stroke.” Updated May 19, 2026. cdc.gov
14. Centers for Disease Control and Prevention. “About Heart Attack Symptoms, Risk, and Recovery.” Updated October 24, 2024. cdc.gov
15. Centers for Disease Control and Prevention. “About Venous Thromboembolism (Blood Clots).” Updated March 5, 2025. cdc.gov