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Testosterone

Testosterone is the best-known androgen (i.e., male hormone), but females produce it too. In both sexes, low testosterone can reduce libido and cause fat gain, muscle loss, and bone loss.

Our evidence-based analysis on testosterone features 177 unique references to scientific papers.

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Summary of Testosterone

Testosterone is a hormone produced primarily in the testes in men, and the ovaries in women, and is relevant to sexual developement, muscle building, fat loss, some aspects of cognition, and hair loss.

Testosterone levels may not tell the whole story of how testosterone is functioning in the body. Your total testosterone can be divided into three categories:

  • Tightly bound testosterone. About two-thirds of the testosterone in your blood is bound to sex hormone binding globulin (SHBG). Your body can’t use it.

  • Loosely bound testosterone. About one-third of the testosterone in your blood is bound to albumin. Your body can use it, but with some effort.

  • Free testosterone. A small percentage of the testosterone in your blood (1–4%, as a rule) just floats around freely. Your body can readily use it, and the enzyme 5-alpha-reductase can convert it to dihydrotestosterone (DHT), a very potent androgen.

Together, your loosely-bound and free testosterone compose your bioavailable testosterone, which has a greater impact on your health than your total testosterone.

Testosterone boosters are supplements that increase your production of testosterone. Supplements that increase only your percentage of free testosterone or DHT are often included in this category.

Aromatase inhibitors

Supplements that inhibit CYP19A1, the aromatase enzyme, are indirect testosterone boosters in men. CYP19A1 serves many purposes, one of which is to convert testosterone to estradiol, the predominant form of estrogen. Inhibiting this enzyme reduces the percentage of testosterone that gets converted to estradiol.

Contrary to what you might think, the male body needs estradiol,[1] though in lesser quantity than women need. When the body detects that estradiol levels are too low, it reacts by increasing its production of the base material it needs to make estradiol: testosterone.

Aromatase inhibitors can boost testosterone on their own, but they can also complement other testosterone boosters. If you take a supplement that increases testosterone without inhibiting the aromatase enzyme (through hypothalamic stimulation, for instance), you may find yourself with more estradiol than you need, a situation that taking an aromatase inhibitor may remedy — if you’re a man, that is. As we saw, aromatase inhibitors hinder the conversion of androgens to estrogens; in premenopausal women, however, ovaries produce most of the estrogen, so aromatase inhibitors are much less effective.

If you are looking for an actual stack of supplements to take, we recommend you look at our increasing testosterone stack.

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Human Effect Matrix

Unlocked for Examine members

The Human Effect Matrix looks at human studies to tell you what supplements affect Testosterone.

Full details on all Testosterone supplements are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Supplement Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
Notes
grade-a Notable High See all 18 studies
There appears to be an increase in testosterone following DHEA supplementation, but the vast majority of literature is in menopausal women (where testosterone contributes to libido). There is variability in the results, and DHEA is unreliable in increasing testosterone, but this unreliability extends to all demographics and subjects (with limited evidence of DHEA increasing testosterone in all studies including youthful athletes, which are less studied).
grade-b
Minor
- See all 9 studies
There appears to be a time-dependent influence on testosterone, with acute doses of alcohol increasing testosterone secondary to creating energy influx in the liver (small enough of an increase to be 'somewhat' effective but may contribute to libido) whereas abuse is known to reduce testosterone levels more notably. The acute increase in testosterone is thought to be related to spikes in libido
grade-b Minor Very High See all 7 studies
Testosterone may be increased in infertile men (who have a reduction in testosterone) and men undergoing strength training, but there is currently no evidence to suggest an inherent testosterone boosting effect in otherwise normal men.

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Frequently Asked Questions and Articles on Testosterone

Does creatine cause hair loss?
It’s plausible, but unlikely. One RCT linked creatine supplementation to an increase in DHT — an androgen involved in hair loss — but this RCT has never been replicated.
How important is sleep?
Sleep is incredibly important, and can be considered crucial alongside diet and exercise. Proper sleep habits help sustain many biological processes, and bad sleep can cause these processes to be suboptimal or even malfunction.
Does ashwagandha increase testosterone?
There is a bit of evidence that shows Ashwagandha increases testosterone, but it is not convincing.
Can creatine increase your testosterone levels?
There is no convincing evidence that creatine can increase your testosterone levels.
How can you increase testosterone naturally?
When it comes to increasing your testosterone, quality sleep, physical activity, and weight management come first. A few supplements can help sustain healthy testosterone levels, but most supplements marketed as testosterone boosters don’t work, though some can make you believe they do by boosting your libido.
Do herbal aphrodisiacs work?
It depends on the product touted to be an aphrodisiac, but some of them do apparently increase sexual desire; it is a relatively under-researched topic though, and we don't know why they increase sexuality.
Four Testosterone Boosters and Sketchy Research
Is semen high in protein?
Yes. Semen is 50% protein by weight and contains a variety of nutrients to protect the sperm cells from damages.
Does ejaculation affect testosterone levels?
Ejaculation results in changes in prolactin (increase) and dopamine (temporary decrease), but does not result in changes in testosterone. Although prolactin and dopamine are both involved with testosterone, they do not appear to influence testosterone levels acutely.
What is 'roid rage'?
Mostly a myth; testosterone (including injections) can increase impulsivity in some but this does not appear to be reliable (does not affect every person tested), impulsivity might lead to aggression but this is drawing at straws now with the connections

Things to Note

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