Semen does contain testosterone, though far less than circulates in blood. It also carries a surprisingly broad mix of other hormones, including estrogen, prolactin, prostaglandins, oxytocin, cortisol and DHEA. The more interesting question is what these chemicals do once semen leaves the body, because some of them act on a partner’s reproductive tract around conception.
How Much Testosterone Is in Semen
Semen is mostly seminal plasma, the fluid part made by the prostate and other glands. Sperm make up only a small share of it. Semen is a blend of secretions from several organs, not a sample of blood, and each gland adds its own chemistry. In men, seminal plasma averaged about 69 ng of testosterone per 100 ml, versus about 487 ng/100 ml in blood.1PubMed. Hormones in seminal plasma That puts semen at roughly one-seventh the testosterone concentration of blood. Other measurements across groups of men found seminal testosterone consistently well below the normal blood range.2PubMed. Follicle-stimulating hormone, luteinizing hormone, and testosterone levels found in human seminal plasma The same pattern shows up in other mammals: cat semen holds about seventeen times less than blood.3Biology of Reproduction. Relationship of Testosterone Concentration in Blood and Seminal Plasma to Sperm Production in Domestic Cat
The testosterone that is there is all free. In blood, about one-third of testosterone is locked onto a carrier protein, but no carrier-bound testosterone was found in seminal fluid.4PubMed. Hormones in seminal plasma
A typical ejaculate is only a few millilitres. With a lower concentration than blood and such a small volume, the total testosterone in one ejaculation is tiny, far below what a medical gel, patch or injection delivers. A partner is not getting a therapeutic dose from contact with semen.
A man cannot judge his own testosterone by how much he ejaculates or how the semen looks. If he suspects low testosterone, the usual route is a blood test arranged by a doctor.
Other Hormones Found in Semen
- Estradiol: the main estrogen, present in the semen of several mammals.5PubMed Central. Absorption and distribution of estradiol from male seminal emissions during mating
- Estrogen’s source: male organs make it with an enzyme that converts testosterone, and fluid inside the testes can reach levels usually seen only in women.6PubMed Central. Estrogens in Male Physiology
- Prolactin: best known for milk production, it is present in semen and appears to help sperm prepare to fertilize an egg.7PubMed. Prolactin in seminal fluid
- Prostaglandins: signaling chemicals that are abundant, with one type at about 46 micrograms per ml.8PubMed. Prostaglandins in semen and their relationship to male fertility: a study of 145 men
- Oxytocin and vasopressin: they occur in tiny amounts, partly made by the prostate.9PubMed Central. Occurrence and reproductive roles of hormones in seminal plasma
- Cortisol and DHEA: the stress hormone and a precursor of sex hormones have also been detected.10PubMed Central. Occurrence and reproductive roles of hormones in seminal plasma
- Pituitary hormones: FSH, LH and growth hormone have been measured in semen.11PubMed Central. Fructose and hormone levels in semen: their correlations with sperm counts and motility
Some of these may be made locally rather than carried over from blood: in healthy fertile men, prolactin levels in seminal plasma differ from blood levels.12PubMed. Seminal fluid prolactin: studies in normal subjects and in hypergonadotropic oligospermia
Estrogen may seem out of place in a male fluid, but it isn’t only a female hormone. Men make it too, largely by converting some of their testosterone. It helps with sperm development in the male reproductive organs, so it has a job there. Finding it in semen is normal and not a sign of a hormone problem or of feminization.
Prostaglandins stand apart from the rest. They appear in semen in amounts thousands of times larger than steroid hormones like testosterone or estrogen, measured in micrograms rather than nanograms. The name comes from the prostate, once thought to be their source, although the seminal vesicles are actually the major source. Unlike classic hormones that travel in the blood to distant organs, they mostly act near where they are released, on nearby muscle and tissue. That local action is one reason researchers study them as signals that could influence the female tract after intercourse.
What Semen Hormones Do in a Partner’s Body
The vaginal wall is thin and rich in blood vessels, and most steroid hormones are readily absorbed through it.13PubMed. Absorption from the vagina They skip the liver’s first breakdown that swallowed drugs face.14PubMed. Absorption from the vagina Some components of semen can be detected in a partner’s bloodstream within a few hours.15PubMed. Does semen have antidepressant properties? That shows some material is absorbed, but not that the amount is enough to change mood or body function.
The clearer effects are local. Seminal fluid switches on genes in the cervix tied to immunity, ovulation and uterine receptivity.16New Scientist. Semen has controlling power over female genes and behaviour It also boosts immune cells that calm inflammation and help the body tolerate an embryo.17PubMed. Seminal fluid and fertility in women In animals these signals can trigger ovulation and support placenta development.18PubMed. The Female Response to Seminal Fluid In women the evidence is still emerging, with an immune response seen in the cervix after intercourse.19PubMed. Seminal fluid and fertility in women
An embryo carries half its genes from the father, so to the mother’s immune system it is partly foreign. If the body treated it like an invader, pregnancy could be threatened. Contact with seminal fluid may help prepare tolerance by shifting immune cells in the cervix toward a calmer response, setting up conditions before a pregnancy begins.
None of this means a woman must be exposed to semen to become pregnant. IVF pregnancies succeed without natural exposure to seminal fluid at the cervix, so priming is not required. Much of the clearest evidence comes from animals, and how strongly these signals matter in women is still being studied.
Does Semen Act as an Antidepressant
The claim traces back to a survey of sexually active college women. Those not using condoms scored lower on a depression questionnaire.20PubMed. Does semen have antidepressant properties? Depressive symptoms rose with more consistent condom use.21PubMed. Does semen have antidepressant properties? Among women not using condoms, scores rose as time since last sex grew.22PubMed. Does semen have antidepressant properties?
Condom use was only a stand-in for semen exposure, not a measurement of it.23PubMed. Does semen have antidepressant properties? Women in steady relationships often stop using condoms, usually when they switch to other contraception or trust a long-term partner, so not using condoms can signal a committed relationship. Stable, supportive relationships are themselves linked to better mood, so the lower scores could reflect the relationship rather than semen. The survey measured both things at one point in time and could not separate them. The only direct test would be a trial giving semen or a placebo and then measuring mood, and none has been done.
The time-since-last-sex pattern could reflect semen, but it could just as easily reflect loneliness, a breakup or reduced intimacy. The idea that absorbed hormones change behavior is a proposed theory, not a tested effect.24PubMed. The intravaginal absorption of male generated hormones and their possible effect on female behaviour
One survey of college women can’t support calling semen an antidepressant. Someone struggling with low mood is better served by established help such as therapy, medication when appropriate, sleep, activity and social support. Avoiding condoms for mood benefits is not supported and raises infection and pregnancy risk.
What Semen Hormones Reveal About Fertility
Infertile men had lower seminal testosterone than men with normal sperm.25PubMed. Assessment of seminal estradiol and testosterone levels as predictors of human spermatogenesis Men with blocked sperm ducts had higher seminal estrogen.26PubMed. Assessment of seminal estradiol and testosterone levels as predictors of human spermatogenesis The local balance of testosterone and estrogen may therefore help sustain sperm production.27PubMed. Assessment of seminal estradiol and testosterone levels as predictors of human spermatogenesis Prolactin, LH and FSH levels in semen rose with sperm count,28PubMed Central. Fructose and hormone levels in semen: their correlations with sperm counts and motility and prostaglandin levels tracked with several measures of male fertility.29PubMed. Prostaglandins in semen and their relationship to male fertility: a study of 145 men In some infertile men, though, the usual prolactin gap between semen and blood was missing.30PubMed. Seminal fluid prolactin: studies in normal subjects and in hypergonadotropic oligospermia
These are associations, not causes. Higher estrogen with blocked ducts suggests the balance may shift when sperm cannot leave, so it may be a result rather than a cause. Hormones that rise with sperm count may simply reflect how active the testes are. The missing prolactin gap hints that local hormone handling may be disrupted, but that is an early observation needing confirmation.
A standard semen analysis counts sperm, checks how well they move and looks at their shape. Hormones are normally measured in a blood sample, because blood tests are well established and have agreed reference ranges. Seminal hormone tests are mostly a research tool, and differences between groups of men don’t yet work as a test for one individual. A man worried about fertility can ask his doctor about a semen analysis and whether blood hormone testing makes sense for him.
How Taking Testosterone Affects Semen
Testosterone treatment lowers the brain signals that tell the testes to make sperm.31PubMed. Effects of testosterone plus medroxyprogesterone acetate on semen quality, reproductive hormones, and germ cell populations in normal young men That is why it is being studied as male contraception, sometimes combined with a progestin.32PubMed. Effects of testosterone plus medroxyprogesterone acetate on semen quality, reproductive hormones, and germ cell populations in normal young men Among men in a fertility clinic using testosterone, 88% had no sperm in their semen, called azoospermia.33PubMed. Testosterone use in the male infertility population: prescribing patterns and effects on semen and hormonal parameters Within 6 months of stopping, 65% without other causes regained sperm production.34PubMed. Testosterone use in the male infertility population: prescribing patterns and effects on semen and hormonal parameters
Sperm production depends on very high testosterone inside the testes, made by the testes themselves. Injected or applied testosterone raises blood levels but doesn’t recreate those concentrations inside the testes, especially once they are no longer being stimulated. Anabolic steroids taken for muscle building can suppress sperm production the same way.
Recovery can take months, so a man shouldn’t expect an immediate return. A repeat semen analysis is the way to see whether sperm have returned, since how a man feels doesn’t show it. Men hoping to conceive should tell their doctor before starting testosterone, and can ask about alternatives that keep sperm production going.