The complete guide
Androgens: How to Raise Testosterone and DHT While Keeping Estrogen and Prolactin Low
Your testes do not decide how much testosterone you have on their own. A brain signal tells them to work, an enzyme in your fat turns their product into estrogen, prolactin and inflammation press the brakes, and a leaky gut can cut testosterone within hours. This page walks through each lever with the studies behind it.
+53%testosterone in one week when estrogen production was blocked in healthy men
2 hfor one dose of endotoxin to lower testosterone in mice, with LH unchanged
−31%diabetes risk for every doubling of DHT, in 852 older men
In this guide
- The map: where testosterone, DHT and estrogen come from
- The chain of command: brain, pituitary, testes
- Testosterone: take the brakes off first
- The gut: how endotoxin shuts down the testes
- DHT: the strongest androgen
- SHBG: how much of your testosterone is free
- Aromatase: keep estrogen low, not zero
- Prolactin: the brake on desire and on the axis
- The protocol in one table
Most advice on testosterone is a list of foods and supplements. The research points to something simpler: the body already knows how to make plenty of it, and in most men something is holding it back. Estrogen, prolactin and inflammation from the gut are the three biggest brakes. Take the brakes off and the numbers move. Below, each section gives the biology first and then the study, with the title or figure from the paper.
The map: where testosterone, DHT and estrogen come from
Every sex hormone starts as cholesterol. A transport protein called StAR carries cholesterol into the mitochondria, where it becomes pregnenolone. From there a short chain of enzymes leads to testosterone. Testosterone then has two exits: 5α-reductase turns it into DHT, the strongest androgen, and aromatase turns it into estradiol.
That gives the whole page in one line: make more testosterone, let more of it become DHT, let less of it become estrogen, keep prolactin in the low-normal range, and stop the gut from leaking endotoxin into the blood.
The study · 4 healthy young men · isotope infusion
Most of a man's estrogen is not made in the testes
Origin of estrogen in normal men and in women with testicular feminizationJ Clin Endocrinol Metab · 1979 · PMID 511978
32 of 44 µgof daily estradiol, at least, was made outside the testes by aromatase in other tissues
What they found
The men made about 5.7 mg of testosterone a day and 44 µg of estradiol. Only 12 µg or less of that estradiol could have come from the testes. The rest was made in other tissues by aromatizing testosterone and androstenedione from the blood.
Keep in mind: Four men, measured in 1979. The point that stands: estrogen in men is mostly a product of conversion, so the tissue that converts (fat above all) controls it.
| Lever | Where you want it | Main brakes | What moved it in studies |
|---|---|---|---|
| Testosterone | High-normal | Estradiol, prolactin, endotoxin, body fat | Blocking estrogen: +53% in a week. Weight loss. |
| DHT | Normal to high | Low 5α-reductase, high prolactin | Zinc in low-zinc men |
| SHBG | Middle of the range | Estrogen pushes it up | A low estrogen dose nearly doubled it in 5 days |
| Estradiol | Low-normal, never zero | Body fat, age, inflammation, endotoxin | Weight loss; aromatase inhibitors (doctor only) |
| Prolactin | Low-normal, never zero | Estrogen, serotonin, low thyroid, tumors | Zinc, vitamin E, treating the thyroid |
| Gut endotoxin | As low as possible | Leaky barrier, body fat | Barrier repair (BPC-157 in rats) |
The chain of command: brain, pituitary, testes
Testosterone is made on orders. The hypothalamus releases GnRH in pulses. Each pulse tells the pituitary to release LH and FSH. LH reaches the Leydig cells in the testes and switches on testosterone production; FSH drives sperm production. Testosterone and estradiol then report back to the brain and slow the signal down when there is enough.
This is why low testosterone has two very different causes. Either the testes are damaged and cannot answer (primary), or the signal from the brain is too weak (secondary). The blood test that tells them apart is LH.
| Testosterone | LH | What it points to | Next tests in the guideline |
|---|---|---|---|
| Low | High | Primary: the testes are not answering a strong signal | Semen analysis, karyotype if indicated |
| Low | Low or normal | Secondary: the signal from the brain is weak | Prolactin, iron studies, other pituitary hormones |
| Normal | Normal | The axis works; look at free testosterone if SHBG is off | SHBG, free testosterone |
The study · Endocrine Society · clinical practice guideline
How low testosterone should be diagnosed
Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice GuidelineJ Clin Endocrinol Metab · 2018 · PMID 29562364
What they found
Diagnose low testosterone only with symptoms plus low levels that are clearly and consistently low. Measure fasting, morning total testosterone with an accurate assay, then repeat it to confirm. If testosterone is near the lower limit, or SHBG is likely to be off, measure free testosterone too.
Keep in mind: Testosterone has a daily rhythm and drops after a meal, so a single afternoon test can make a normal man look low. More on testing in the labs guide.
Testosterone: take the brakes off first
In most men with low testosterone the testes are fine. The brakes are on. The biggest single brake in modern men is body fat, because fat tissue is where aromatase lives and where gut endotoxin builds up. Two studies show the size of the effect.
The study · Lean vs obese young men
Obese men had 44% less testosterone and twice the estradiol
Enhanced conversion of androstenedione to estrogens in obese malesJ Clin Endocrinol Metab · 1980 · PMID 7419688
What they found
Testosterone fell from 5.89 ng/mL in lean men to 3.29 ng/mL in obese men, while estradiol rose from 21.7 to 43.9 pg/mL. The more a man weighed, the more of his androgens were converted into estrogens: the correlation with body weight was r = 0.93.
Keep in mind: A comparison between groups, not an intervention. The weight-loss meta-analysis below tests the direction.
The study · Meta-analysis · 24 studies
Losing fat raises testosterone, and the more you lose the more it rises
Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysisEur J Endocrinol · 2013 · PMID 23482592
+8.7 nmol/Ltotal testosterone after bariatric surgery, against +2.9 nmol/L with a low-calorie diet
What they found
Both diet and surgery raised total and free testosterone and lowered estradiol, and LH and FSH went up. The amount of weight lost was the best predictor of how much testosterone rose. Younger, non-diabetic and heavier men gained the most.
Keep in mind: 8.7 nmol/L is about 250 ng/dL, and 2.9 nmol/L about 83 ng/dL.
So the first lever is not a supplement. It is the fat tissue that converts testosterone into estrogen, and, as the next section shows, the endotoxin that comes with it.
The gut: how endotoxin shuts down the testes
Endotoxin, or lipopolysaccharide (LPS), is part of the outer wall of many gut bacteria. A healthy gut keeps it inside. When the gut barrier is irritated or leaky, small amounts pass into the blood. This is called metabolic endotoxemia, and it rises with body fat and a high-fat, high-calorie diet. The immune system answers with inflammation, and the testes are one of the first organs to pay. Background on endotoxin in Ray Peat on endotoxin.
The study · Theory paper
GELDING: Gut Endotoxin Leading to a Decline IN Gonadal function
Gut Endotoxin Leading to a Decline IN Gonadal function (GELDING) - a novel theory for the development of late onset hypogonadism in obese menBasic Clin Androl · 2016 · PMID 27340554
What they found
The proposal: obesity and a high-fat, high-calorie diet change the gut bacteria and make the gut wall leakier. Endotoxin then enters the blood and lowers testosterone two ways, directly in the Leydig cells and indirectly by weakening the LH signal from the pituitary.
The study · 75 men, then an endotoxin test in lean men
More endotoxin, less testosterone, and a dose of it proved the direction
Endotoxin-initiated inflammation reduces testosterone production in men of reproductive ageAm J Physiol Endocrinol Metab · 2018 · PMID 29183872
What they found
Men with more endotoxin exposure (measured as LBP) had lower testosterone and higher IL-6, and IL-6 went with lower free testosterone. Then lean men were given a small dose of endotoxin: a short burst of inflammation was followed by a fall in testosterone, while LH and FSH did not change. The testes, not the brain, took the hit.
Keep in mind: An earlier study by the same group in 50 men found the same pattern: more body fat, more endotoxin, less testosterone (Tremellen 2017).
The study · Male rats · 2 hours
Endotoxin turned androgens into estrogens, and an aromatase inhibitor stopped it
Effect of the aromatase inhibitor, 4 hydroxyandrostenedione, on the endotoxin-induced changes in steroid hormones in male ratsLife Sci · 1992 · PMID 1573977
What they found
Two hours after endotoxin, estrogens shot up and androgens dropped. A single dose of the aromatase inhibitor 4OHA blocked this in a dose-dependent way, and the highest dose blocked all of the sex-steroid changes. Endotoxin works partly by switching aromatase on.
The study · Mice · Leydig cells
Endotoxin damages the mitochondria where testosterone is made
Bacterial endotoxin lipopolysaccharide and reactive oxygen species inhibit Leydig cell steroidogenesis via perturbation of mitochondriaEndocrine · 2004 · PMID 15758255
What they found
One injection of endotoxin lowered testosterone within 2 hours. StAR and 3β-HSD, two proteins the Leydig cell needs to make testosterone, fell. The cell membranes showed oxidative damage and the mitochondria were disrupted, with a large drop in their membrane potential. Hydrogen peroxide alone did the same, pointing to reactive oxygen species from testicular macrophages.
The study · Mice · testes and adrenals
Same toxin, opposite orders: stress hormones up, testosterone down
Diametric effects of bacterial endotoxin lipopolysaccharide on adrenal and Leydig cell steroidogenic acute regulatory proteinEndocrinology · 2000 · PMID 11089530
What they found
Endotoxin lowered testosterone within 2 hours with no change in LH, LH receptors or cAMP. StAR protein fell in the Leydig cells and rose in the adrenal glands. Under endotoxin the body moves cholesterol away from sex hormones and toward stress hormones.
The brain gets the message too. In a review of how infection controls the pituitary, IL-1 blocked the release of GnRH and so the LH pulses, without touching FSH (McCann 1997). And endotoxin is one of the strongest triggers of serotonin release in the gut, which feeds the prolactin brake further down.
Closing the barrier: where BPC-157 fits
If endotoxin from the gut is a brake on the testes, the gut barrier is a lever. BPC-157 is a 15-amino-acid peptide taken from a protein in human gastric juice. It is stable in stomach acid, which is why it is studied by mouth, and it reached phase II trials for inflammatory bowel disease as PL 14736 (Sikiric 2012). The animal work on the gut is broad:
The study · Rats · colitis from a cut blood supply
BPC-157 saved the colon lining after its blood supply was cut
Stable gastric pentadecapeptide BPC 157 in the treatment of colitis and ischemia and reperfusion in rats: New insightsWorld J Gastroenterol · 2017 · PMID 29358856
What they found
A bath of BPC-157 on the starved colon segment brought blood vessels back within minutes, kept oxidative stress (MDA) and nitric oxide normal, and preserved the mucosal folds. By day 10 the treated colons had an almost completely spared lining.
The study · Rats · stomach-to-skin fistulas
Stomach fistulas closed, better than with standard ulcer drugs
Therapy for unhealed gastrocutaneous fistulas in rats as a model for analogous healing of persistent skin wounds and persistent gastric ulcers: stable gastric pentadecapeptide BPC 157, atropine, ranitidine, and omeprazoleDig Dis Sci · 2009 · PMID 18649140
What they found
BPC-157 in drinking water or by injection healed both the stomach defect and the skin wound and closed the fistulas, also in rats given a corticosteroid that slows healing. It did better than the standard ulcer drugs atropine, ranitidine and omeprazole.
- Colon-to-skin fistulas healed, by mouth or injection, through the nitric oxide system (Klicek 2008).
- Perforated cecum: vessels came back, bleeding shortened and oxidative stress stayed normal (Drmic 2018).
- Duodenum-to-colon fistulas closed on both sides, with no leakage, while controls kept leaking and lost weight (Sikiric 2024).
- Stomach lesions from alcohol and other irritants were prevented (Sikiric 1996).
The full BPC-157 evidence, with every study card, is in the BPC-157 guide. The gut side is in BPC-157 and leaky gut, and the food side in how to fix a leaky gut.
BPC-157 CapsulesView productDHT: the strongest androgen
DHT is testosterone with one double bond removed by 5α-reductase. It binds the androgen receptor more tightly than testosterone and it cannot be turned into estrogen. It is made mostly in tissues such as skin, the prostate and hair follicles. It has a bad name because of hair loss, but the studies on what DHT does in the body as a whole tell a different story.
The study · Men born without working 5α-reductase
Without DHT, the male body does not form properly
Steroid 5alpha-reductase deficiency in man: an inherited form of male pseudohermaphroditismScience · 1974 · PMID 4432067
What they found
Men with an inherited loss of 5α-reductase had very low DHT. Before birth this left the external genitalia incompletely masculinized, even though testosterone itself was there.
The study · 852 older men · followed for 9.8 years
More DHT went with less insulin resistance and less diabetes
Testosterone, Dihydrotestosterone, Sex Hormone-Binding Globulin, and Incident Diabetes Among Older Men: The Cardiovascular Health StudyJ Clin Endocrinol Metab · 2017 · PMID 27732332
−31%risk of diabetes for every doubling of total DHT (hazard ratio 0.69)
What they found
In the Cardiovascular Health Study, higher DHT measured by mass spectrometry was linked to lower insulin resistance and fewer new cases of diabetes. Free testosterone was not.
Keep in mind: An association in older men, not proof that raising DHT prevents diabetes.
The study · Placebo-controlled · healthy men
Finasteride cuts DHT and leaves estradiol and LH alone
Effects of finasteride (MK-906), a 5 alpha-reductase inhibitor, on circulating androgens in male volunteersJ Clin Endocrinol Metab · 1990 · PMID 2156887
What they found
Finasteride lowered DHT at every dose tested, from 0.04 mg to 100 mg a day. Testosterone rose at the higher doses; LH, FSH, cortisol and estradiol did not change. DHT came back within 14 days of stopping.
Keep in mind: This is the drug sold for hair loss. What it does to mood and sexual function is covered in DHT blocker side effects.
What raised DHT in studies
The study · 37 infertile men · no placebo group
Zinc raised DHT, and testosterone in the men who started low
Effect of zinc administration on plasma testosterone, dihydrotestosterone, and sperm countArch Androl · 1981 · PMID 7271365
What they found
In the 22 men with low testosterone, testosterone rose from 3.50 to 5.40 ng/mL, DHT from 0.38 to 0.50 ng/mL, and sperm count from 8 to 20 million/mL. Nine of their wives became pregnant. In the 15 men with normal testosterone, only DHT rose (0.48 to 0.57 ng/mL).
Keep in mind: No placebo group, and the men were infertile. Zinc helps most where zinc or testosterone is low.
The study · 6 healthy men
Raising prolactin blocked the conversion of testosterone to DHT
Study on the relationship between plasma prolactin levels and androgen metabolism in manJ Clin Endocrinol Metab · 1976 · PMID 977731
What they found
The men took sulpiride for 4 days to raise prolactin, then got an hCG shot to stimulate the testes. Testosterone rose as usual, but the DHT rise was much smaller than without high prolactin. The authors concluded prolactin interferes with 5α-reductase.
More on food, training and supplements for DHT in how to increase DHT.
SHBG: how much of your testosterone is free
Most testosterone in the blood is carried by proteins. SHBG holds it tightly; albumin holds it loosely and lets it go to tissues. Only a small fraction floats free. Two men with the same total testosterone can have very different amounts available, depending on SHBG.
- Bound to SHBG ~44%
- Bound to albumin ~50%
- Other proteins ~4%
- Free ~2%
The study · Binding model · human plasma
The study behind the 2% free testosterone number
Transport of steroid hormones: binding of 21 endogenous steroids to both testosterone-binding globulin and corticosteroid-binding globulin in human plasmaJ Clin Endocrinol Metab · 1981 · PMID 7195404
What they found
Dunn and colleagues measured how strongly 21 steroids bind to SHBG, CBG and albumin and calculated how each one is split in the blood of men and women. In men, testosterone came out at about 44% on SHBG, about half on albumin, and about 2% free.
The study · 8 healthy men · 5 days
A small dose of estrogen nearly doubled SHBG in five days
Effects of ethinyloestradiol on plasma levels of pituitary gonadotrophins, testicular steroids and sex hormone binding globulin in normal menClin Endocrinol (Oxf) · 1981 · PMID 6790203
≈2×SHBG binding after 5 days of 30 µg ethinyl estradiol a day
What they found
LH and testosterone first dropped, then climbed back, but SHBG went up by almost 100%, so the free testosterone index fell. Estrogen locks testosterone away, on top of slowing LH.
Keep in mind: SHBG is not purely the enemy: in the diabetes study above, higher SHBG went with lower insulin resistance. Aim for the middle of the range.
Aromatase: keep estrogen low, not zero
Aromatase turns testosterone into estradiol and androstenedione into estrone. In men it works mostly outside the testes: in fat, skin, bone and the brain. Estradiol is the strongest brake on the whole axis. It slows GnRH pulses in the brain, makes the pituitary less responsive, and acts on the Leydig cells directly.
The study · Healthy men · aromatase blocked for 7 days
Block estrogen and testosterone rises by half
Aromatase inhibition in the human male reveals a hypothalamic site of estrogen feedbackJ Clin Endocrinol Metab · 2000 · PMID 10999781
+53%testosterone after 7 days of anastrozole, as estradiol fell from 136 to 52 pmol/L
What they found
LH roughly doubled. The brain sent more LH pulses (10.2 to 14.0 a day) and each pulse was bigger (5.7 to 8.4 IU/L). Estrogen brakes the axis at two levels: the hypothalamus and the pituitary.
Keep in mind: They used 10 mg of anastrozole a day, ten times the usual medical dose, to study the mechanism. This is not a dose anyone should copy.
The study · Healthy young men · one injection
One shot of estradiol cut testosterone by 84% in 36 hours
Direct inhibition of Leydig cell function by estradiolJ Clin Endocrinol Metab · 1978 · PMID 122429
What they found
After a single 2 mg injection of estradiol, testosterone fell from 760 to 295 ng/dL at 24 hours and to 123 ng/dL at 36 hours. LH and FSH did not fall in the same way, so the authors concluded estradiol was blocking the enzymes inside the Leydig cell directly.
The study · 10 healthy men · letrozole plus estradiol patches
Testosterone moved opposite to estradiol
In men, peripheral estradiol levels directly reflect the action of estrogens at the hypothalamo-pituitary level to inhibit gonadotropin secretionJ Clin Endocrinol Metab · 2006 · PMID 16787981
What they found
With aromatase blocked and estradiol added back in falling doses, mean testosterone ranged from 179 to 955 ng/dL. Testosterone, LH and FSH were inversely related to estradiol in the blood.
The study · 3 patients · New England Journal of Medicine
Too much aromatase, from birth: breasts and shut-down testes
Estrogen excess associated with novel gain-of-function mutations affecting the aromatase geneN Engl J Med · 2003 · PMID 12736278
What they found
A father, his son and an unrelated boy had a genetic change that switched aromatase on in many tissues. They had severe gynecomastia and low LH-driven testosterone. An aromatase inhibitor lowered estrogen and brought LH, FSH and testosterone back to normal.
What switches aromatase on
| Switch | What the study showed | Study |
|---|---|---|
| Body fat | Conversion of androgens to estrogens rose with body weight in obese men | Kley 1980 |
| Age | Aromatase activity per fat cell rose with age (fat from women) | Cleland 1985 |
| Inflammation (PGE2) | PGE2 from COX-2 switched aromatase on, and estradiol switched COX-2 on again | Bulun 2000 |
| Endotoxin | Estrogens up and androgens down within 2 hours, blocked by an aromatase inhibitor (rats) | Christeff 1992 |
| Genes | A rare mutation left aromatase switched on everywhere | Shozu 2003 |
The study · Randomized, double-blind · 23 obese men with low testosterone
Weight loss plus an aromatase inhibitor beat weight loss alone on hormones
Aromatase Inhibitors Plus Weight Loss Improves the Hormonal Profile of Obese Hypogonadal Men Without Causing Major Side EffectsFront Endocrinol (Lausanne) · 2020 · PMID 32499757
What they found
All men dieted and exercised for 6 months; half also took 1 mg of anastrozole a day. That group ended with higher testosterone, lower estradiol and more fat loss. Strength and symptoms did not improve more than with weight loss alone.
Keep in mind: Better numbers did not mean the men felt better. An aromatase inhibitor is a drug for a doctor to decide on.
The study · 400 healthy men · New England Journal of Medicine
Why estrogen should be low, not gone
Gonadal steroids and body composition, strength, and sexual function in menN Engl J Med · 2013 · PMID 24024838
What they found
With testosterone and estrogen production switched off and given back in controlled doses, the loss of testosterone took away lean mass, muscle and strength. The loss of estrogen is what drove the gain in body fat. Both contributed to lower sexual desire.
The exit: the liver and the gut
Estrogen leaves the body through the liver, which packages it and sends it into the bile. In the gut, bacterial β-glucuronidase can unpack it so it is absorbed again. Fiber and a healthy gut send more of it out.
The study · 20 women · four 3-day periods
More fiber, more estrogen out in the stool, less in the blood
Estrogen excretion patterns and plasma levels in vegetarian and omnivorous womenN Engl J Med · 1982 · PMID 7144835
What they found
The vegetarian women ate 28 g of fiber a day against 12 g. They excreted more estrogen in the stool, their gut bacteria had lower β-glucuronidase activity, and the more estrogen they excreted the lower their blood estrone and estradiol.
Keep in mind: A study in women, but the exit route is the same in men.
Prolactin: the brake on desire and on the axis
Prolactin is best known for milk production, but in men it acts as a brake. High prolactin slows the GnRH pulses, so LH, FSH and testosterone all fall. In a clinical review it was found in 16% of men with erectile dysfunction and about 11% of men with low sperm counts (De Rosa 2003).
The study · 3,101 men at a fertility clinic
Men with high prolactin had lower testosterone and a fifth of the motile sperm
Prevalence of Hyperprolactinemia and Clinically Apparent Prolactinomas in Men Undergoing Fertility EvaluationUrology · 2022 · PMID 33766719
What they found
2.1% of the men had high prolactin. Their median testosterone was 280 against 313 ng/dL, their total motile sperm count 7.0 million against 34.7 million, and 43% had low sperm counts against 22%.
| Cause | What the study showed | Study |
|---|---|---|
| Estrogen | Lowering estradiol in healthy men lowered prolactin | D'Agata 1982 |
| Serotonin | Serotonin activity raised prolactin in rats | Clemens 1977 |
| Low thyroid | Treating the thyroid fixed high prolactin in most cases | Khan 2025 |
| Dopamine-blocking drugs | Sulpiride was used to raise prolactin on purpose | Magrini 1976 |
| Pituitary tumor | Prolactinomas; treated with dopamine drugs by a doctor | De Rosa 2003 |
The study · 6 healthy men · aromatase inhibitor
Less estradiol, less prolactin
Hydrotestolactone lowers serum oestradiol and PRL levels in normal men: evidence of a role of oestradiol in prl secretionClin Endocrinol (Oxf) · 1982 · PMID 7172459
What they found
When an aromatase inhibitor lowered estradiol from 68 to 26 pmol/L, prolactin fell from 11.2 to 6.5 ng/mL, in every man. Estrogen is one of the things that keeps prolactin up.
Serotonin is the other big driver, and most serotonin is made in an irritated gut. The full story is in the serotonin guide.
What lowered prolactin in studies
The study · 17 healthy adults · single doses
Zinc lowered prolactin within two hours
Zinc: an inhibitor of prolactin (PRL) secretion in humansHorm Metab Res · 1989 · PMID 2753470
What they found
Doses of 25, 37.5 and 50 mg of zinc by mouth lowered prolactin below baseline in every subject as blood zinc rose.
Keep in mind: A short-term effect from single doses.
The study · Randomized · dialysis patients
Vitamin E cut very high prolactin by 70%
Effect of vitamin E therapy on sexual functions of uremic patients in hemodialysisInt J Artif Organs · 1992 · PMID 1490755
50.8 → 15.4ng/mL prolactin after 8 weeks of 300 mg vitamin E a day
What they found
Prolactin fell in the vitamin E group and not in the placebo groups. FSH, LH and free testosterone did not change.
Keep in mind: Patients on dialysis, whose prolactin was very high. Healthy men have not been tested this way.
The study · Systematic review · 804 patients
Fix the thyroid and high prolactin often goes away
Systematic review of the association between thyroid disorders and hyperprolactinemiaThyroid Res · 2025 · PMID 39754184
70%of patients with full data had prolactin back to normal after thyroid treatment
What they found
Low thyroid is a common cause of high prolactin. The higher the TSH, the higher the prolactin. When the thyroid was treated, 38 of 54 patients had complete resolution and 10 more improved.
Keep in mind: Most patients were women. If your prolactin is high, ask for TSH as well.
The study · 2,948 men aged 40 to 79
Too little prolactin is not good either
Low prolactin is associated with sexual dysfunction and psychological or metabolic disturbances in middle-aged and elderly men: the European Male Aging Study (EMAS)J Sex Med · 2014 · PMID 24345293
What they found
Lower prolactin went with worse sexual function, less enjoyment of orgasm, more depressive symptoms, and more metabolic syndrome.
Keep in mind: Association only. The target is low-normal prolactin, not the lowest number a drug can reach.
More on prolactin, thyroid and testosterone in prolactin, the anti-life hormone.
The protocol in one table
Ordered from the biggest, safest lever to the ones that need a doctor.
| Step | Why | Evidence |
|---|---|---|
| 1. Test properly | Fasting morning total testosterone, twice. Add LH, estradiol, SHBG, prolactin and TSH | Bhasin 2018 |
| 2. Lose excess fat | Fat is where aromatase and endotoxin build up | Corona 2013, Kley 1980 |
| 3. Calm the gut | Less endotoxin means less brake on the testes; fiber carries estrogen out | Tremellen 2018, Goldin 1982 |
| 4. Zinc, if low | Raised testosterone and DHT in low-testosterone men; lowered prolactin | Netter 1981, Brandão-Neto 1989 |
| 5. Vitamin E | Lowered very high prolactin | Yeksan 1992 |
| 6. Check the thyroid | Low thyroid is a common cause of high prolactin | Khan 2025 |
| 7. Drugs, with a doctor | Aromatase inhibitors and dopamine drugs work on numbers, not always on symptoms | Colleluori 2020, De Rosa 2003 |
Quick answers
How do I raise testosterone naturally?
Start with the brakes. Excess body fat converts testosterone into estrogen and carries more gut endotoxin; losing it raised testosterone in a meta-analysis of 24 studies, more with more weight lost. Then check prolactin, thyroid and zinc status, and look after the gut barrier.
Should I take an aromatase inhibitor to raise testosterone?
Not on your own. They do raise testosterone, but men need some estrogen: in a large NEJM study, losing estrogen drove fat gain and lowered desire. In a trial in obese men, an inhibitor improved the numbers but not strength or symptoms.
Can prolactin be too low?
Yes. In 2,948 men in the European Male Ageing Study, low prolactin went with worse sexual function, depressive symptoms and metabolic syndrome. The aim is low-normal, not as low as possible.
How does a leaky gut lower testosterone?
Endotoxin from gut bacteria enters the blood, damages the testosterone-making mitochondria in the Leydig cells, switches aromatase on, and blocks GnRH in the brain. In lean men, a small endotoxin dose lowered testosterone without changing LH.
Does BPC-157 raise testosterone?
No study has tested that. BPC-157 repaired gut injuries in many rat studies. The link to testosterone is indirect: a tighter gut barrier should mean less endotoxin, which is a known brake on the testes.
The studies
- Origin of estrogen in normal men and in women with testicular feminizationJ Clin Endocrinol Metab · 1979 · PMID 511978
- Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice GuidelineJ Clin Endocrinol Metab · 2018 · PMID 29562364
- Enhanced conversion of androstenedione to estrogens in obese malesJ Clin Endocrinol Metab · 1980 · PMID 7419688
- Body weight loss reverts obesity-associated hypogonadotropic hypogonadism: a systematic review and meta-analysisEur J Endocrinol · 2013 · PMID 23482592
- Steroid 5alpha-reductase deficiency in man: an inherited form of male pseudohermaphroditismScience · 1974 · PMID 4432067
- Testosterone, Dihydrotestosterone, Sex Hormone-Binding Globulin, and Incident Diabetes Among Older Men: The Cardiovascular Health StudyJ Clin Endocrinol Metab · 2017 · PMID 27732332
- Effects of finasteride (MK-906), a 5 alpha-reductase inhibitor, on circulating androgens in male volunteersJ Clin Endocrinol Metab · 1990 · PMID 2156887
- Effect of zinc administration on plasma testosterone, dihydrotestosterone, and sperm countArch Androl · 1981 · PMID 7271365
- Study on the relationship between plasma prolactin levels and androgen metabolism in manJ Clin Endocrinol Metab · 1976 · PMID 977731
- Transport of steroid hormones: binding of 21 endogenous steroids to both testosterone-binding globulin and corticosteroid-binding globulin in human plasmaJ Clin Endocrinol Metab · 1981 · PMID 7195404
- Effects of ethinyloestradiol on plasma levels of pituitary gonadotrophins, testicular steroids and sex hormone binding globulin in normal menClin Endocrinol (Oxf) · 1981 · PMID 6790203
- Aromatase inhibition in the human male reveals a hypothalamic site of estrogen feedbackJ Clin Endocrinol Metab · 2000 · PMID 10999781
- Direct inhibition of Leydig cell function by estradiolJ Clin Endocrinol Metab · 1978 · PMID 122429
- In men, peripheral estradiol levels directly reflect the action of estrogens at the hypothalamo-pituitary level to inhibit gonadotropin secretionJ Clin Endocrinol Metab · 2006 · PMID 16787981
- Estrogen excess associated with novel gain-of-function mutations affecting the aromatase geneN Engl J Med · 2003 · PMID 12736278
- Effects of aging and obesity on aromatase activity of human adipose cellsJ Clin Endocrinol Metab · 1985 · PMID 3964790
- Estrogen biosynthesis in endometriosis: molecular basis and clinical relevanceJ Mol Endocrinol · 2000 · PMID 10915216
- Effect of the aromatase inhibitor, 4 hydroxyandrostenedione, on the endotoxin-induced changes in steroid hormones in male ratsLife Sci · 1992 · PMID 1573977
- Aromatase Inhibitors Plus Weight Loss Improves the Hormonal Profile of Obese Hypogonadal Men Without Causing Major Side EffectsFront Endocrinol (Lausanne) · 2020 · PMID 32499757
- Gonadal steroids and body composition, strength, and sexual function in menN Engl J Med · 2013 · PMID 24024838
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