The Testicles and Scrotum

The testicles and scrotum

In case you don't know what your insides look like, here they are:

The testicles (aka "testes", a word I think you hear more in Europe than America) are remarkable organs. They live outside the body because sperm production can only take place in a slightly cooler environment than that of the body cavity.

They produce sperm - about 150 million every 24 hours - and they keep the body well supplied with testosterone, that scourge of womanhood, the hormone responsible for men's sexiness, body hair, odor, erections, sexual libido and many of the other things that make a man a man, so to speak. And of all of the hundreds of millions of sperm they produce in a lifetime, only a very few will ever fertilize a woman's egg. You may well ask, why such overcapacity? A good question, which I shall try and answer on on this page.

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Male arousal and desire
Andropause: low testosterone
Orgasm and ejaculation
Male initiation: rites of passage
All about semen
The testicles and scrotum
Mature masculinity
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Penile and genital piercing
Causes & Cures: Premature Ejaculation

The testicles are undoubtedly vulnerable, hanging outside the body in the scrotum, and it seems remarkable that they are damaged so infrequently, given the male propensity for sport and fighting. Maybe their resilience is a testimony to their great design! So, what do they do, and how do they work?

Sidebar: Sexual dysfunction affects many men in one form or another, the most common problems being erectile dysfunction and premature ejaculation. However, solutions for both these problems are easily available. Check out the advice at stop premature ejaculation now for practical strategies to solve this problem.

What do testicles do?

They make testosterone and they make sperm. They do this in different parts of the testicle - the sperm are made by "germ" cells in the seminiferous tubules; the testosterone by Leydig cells which occupy the spaces between the tubules. The sperm-producing part of the testicle occupies about 60 to 80% of its volume in the human male.

So tightly twirled up are the seminiferous tubules, that if you uncoiled them, each testis would contain, on average, about 360 meters (nearly 1200 feet) of these tubules, all of which is lined with sperm producing tissue. This astonishing fact means that the average pair of testicles produces about 150 million sperm a day; overall, the testicles contain about two billion sperm at any one time.

The process of sperm production - the transformation of normal cells into mobile, tail-lashing swimmers with only one set of chromosomes - is a remarkable one which involves six stages of development; perhaps even more remarkable is the fact that when a man's fertility is impaired because he cannot produce sperm able to swim, doctors can now extract sperm at an earlier stage of development from his testicle and inject them straight into the egg, thereby overcoming the capriciousness of nature.

What, you may ask, happens to sperm that never make it to the outside world? The answer is that the body has a mechanism by which other cells destroy them, rather in the manner that foreign cells invading the body are destroyed by the white blood cells of the immune system.

Making babies

It is a strange paradox that even though the body produces so many sperm, many couples (about 10%) may have trouble conceiving; there can be many reasons for this, of course, and the opinion of a specialist is always necessary.

Like most people, I certainly know some couples who have conceived on their first try, while other have not succeeded despite their best efforts. This raises the question of what is normal? (Or average?)

If a young couple who are both normally fertile plan a pregnancy, it will occur within 3 months in 75% of couples. In the population as a whole (taking into account those couples whose fertility is less than normal, for any reason), 70% will conceive within the first 6 months of unprotected sex, and 90% will be pregnant within 12 months. But the expected success rate drops steadily as the female partner gets older: one study suggested that for women over 25 years of age, only 80% would be pregnant within 20 months.

Another peculiar fact which might be of interest to anyone trying for a child is that the frequency of sex does have a bearing on the success rate: the optimum for a fully fertile couple trying to get pregnant is 3 or 4 times a week. And while we're on the subject, most conceptions take place on the day of ovulation or the two days beforehand.

I can't resist these little curiosities: in humans, the sex ratio of boys to girls at birth is biased by about 1 to 3% towards the male sex. But this is not a constant ratio - in Germany, both world wars had a tremendous impact on the number of boys born, which went up very significantly. The reason appears to be that the sex at birth is very influenced by the time of conception: most boys are born when conception is early or late in the cycle of possible fertile days in a woman's cycle.

Social scientists have suggested that the much higher frequency of intercourse on combat leave led to much more fertilization in the early stages of the woman's cycle, and hence the higher number of boys born. It is of course a happy coincidence that such a mechanism replaces the males that society has lost through war.

As you may recall from Biology 101, each cell in the human body contains 23 pairs of chromosomes. These pairs unwrap into single chromosomes in the egg and the sperm, and then combine again when the egg is fertilized to produce a new set of 23 pairs of chromosomes in the offspring.

Because the unwrapping process involves some exchange of genetic material between the two members of each chromosomal pair in the man's testicles and the woman's eggs, and because each member of a pair of chromosomes may not carry the same genes, there is the opportunity for genetic reassortment and variation between parents and children.

I guess everyone knows that. But there may be more genetic variation going on than a lot of people realize: many studies have consistently found that fathers who accept paternity are often not the biological father: indeed, up to 10 per cent of children in one study in the central USA were fathered by someone other than their supposed father. I suppose it would be easy to draw a crude parallel with our animal ancestry, but I won't.

No, on second thoughts, I will. In the animal kingdom, where a female produces offspring that need long-term care - like human offspring - she may be better off with a long-term pair bond, with a male who can protect and provide for the offspring.

However, biologically, she is under pressure to mate with the highest ranking male possible in the society (to incorporate the more successful males' qualities into her offspring, so that they have a better chance of survival) - and this may not be the same male as her long term partner. I suppose we are still pretty much at the whim of our ancestry, if we care to let it get the better of us.

The development of the testicles

There seems to be a common myth that a boy's balls drop at puberty. But this is simply wrong. The testicles begin their descent into the scrotum at week 28 of pregnancy, and the process is complete in 97% of boys by 12 weeks after birth. Testicles that don't descend can be problematic: sperm production can be disturbed, and if they remain in the abdomen, there is an increased risk of testicular cancer.

This may have something to do with the temperature of the testicles: in men, they are about 3 to 5 degrees Centigrade cooler than the abdominal temperature, and about one and a half degrees warmer than the skin of the scrotum. It is not known why this should be with any certainty.

Sperm production begins at puberty, not surprisingly, and depends on a complicated interrelationship of hormonal influences in the male body. One of these is the appropriate level of testosterone - too much testosterone acts as a negative feedback control on the hypothalamus and prevents the brain from producing the hormones necessary for spermatogenesis, and therefore acts like a male contraceptive.

Long-acting testosterone-like compounds are indeed the basis of several products undergoing trials as male contraceptives at the moment.

One of the side effects of testosterone replacement therapy, therefore, is that a man may become, at least temporarily, infertile and his testicles shrink. These changes are reversible when the testosterone regime is stopped, except when the supplement are administered in such extreme doses as to bear no relationship to normality. Thus, body builders who take testosterone in excessively high doses may find when they reduce the supplements that they have permanently damaged their body's ability to restore a natural hormonal balance. There are some references on this in the links table below.

How big are adult testicles? The orchidometer is a device used by doctors to measure boys' and adult males' testicles. A grown man's testicles are generally between 16 and 27 milliliters in volume, and about an inch and a half long. If you click here, you can see an orchidometer in plan (the actual thing is a series of egg shaped plastic balls on a string, which the doctor compares to the testicle size).

Apparently for some reason, in eighty percent of men the left testicle - as you face forwards - is the bigger and lower. I don't know if it produces more sperm than its smaller brother. The sperm output from the testicles is mixed and stored in the epididymis before being mixed with fluid from the seminal vesicles and prostate and launched into the big wide world.

Each ejaculation, which is usually between 2 and 6 milliliters in volume (but you can make it more - see the page on ejaculation) contains about 100 million sperm. This means that the sperm occupy no more than 2 or 3 per cent of the volume of each ejaculation. Amazing.

Testicle structure & ejaculation - the journey of sperm to egg

There's a picture at the top of this page of a cross-section of the male reproductive system. The seminiferous tubules in which sperm are manufactured run up through the testis and into the epididymis, which stores the sperm for an average of between 2 and 11 days, although sperm can live in it for up to two weeks. (After about two weeks of abstinence, sperm are passed out in a man's urine.) Various secretions will keep the sperm alive in the epididymis but less active than they will be after ejaculation. Semen is made up of the sperm passed from the epididymis and the secretions of the glands of the reproductive tract. During sexual arousal and ejaculation, secretions are released first by the Cowper's glands (aka bulbourethral glands), then by the prostate and epididymis, and then the seminal vesicles. The Cowper's glands produce a secretion that neutralizes urine or acidity in the urethra; the epididymis and prostate add sperm and enzymes, and finally the seminal vesicles contract and expel the greatest amount of liquid and spermatozoa. The finished liquid is a mixture of sperm, zinc, citric acid, various enzymes, PSA, and fructose, that is first passed into the urethra by action of the sympathetic nervous system, and then forcibly expelled from the body at the moment of ejaculation by contraction of the bulbocavernosal muscles which lie at the base of the penis and the urethral passage.

The semen coagulates when ejaculated, then liquefies some time later (within 20 to 30 minutes). The journey of sperm along the female vagina and oviduct to the egg is a remarkable one which starts when the coagulated semen liquefies in a woman's vagina. The sperm then begin to migrate along her vagina towards the cervix.

The cervix is lined with a mucus, one function of which is to stop abnormal sperm getting through, although some couples may have a problems with fertility because the woman's cervical mucus also reacts against healthy sperm. The presence of prostaglandins in the man's semen has a powerful effect on the vaginal tract, causing movements which assist the passage of sperm in bulk towards the uterus (aka "womb"). It has also been suggested that the female orgasm is a powerful aid to fertilization, enhancing the passage of sperm into the uterus - there is a reference on this "Upsuck Theory" below.

Anyway, once in the uterus, the sperm generally still have to get into the Fallopian tubes before they can fertilize an egg: and there is some evidence that the composition of fluids in the female system is such that only at the time of ovulation can sperm travel freely into the tubes. Be that as it may, of the 40 million or so sperm in each intravaginal ejaculation, only 200 or so will get as far as the Fallopian tube and be in with a chance of fertilizing the egg: this really is a case of survival of the fittest!

And even when they do get there, they still have to penetrate the egg, and there is evidence that to do this they need to be able to thrash much more vigorously than they did when swimming up the vaginal tract. If the sperm do not have the energy left, or are incapable of producing it, the poor things will not penetrate the egg. There are many causes of male infertility, but it is fair to say that the difficulties of getting into the egg, which involves a complex chemical reaction of many stages, is a prime cause.

After the sperm has entered the egg, and the genetic material of male and female has fused, so as to restore the 23 pairs of chromosomes that will carry all the genetic inheritance of the new offspring, the fertilized egg is swept along to the uterus. It spends 3 days free before implanting into the wall of the uterus, an event that takes place about 6 or 7 days after fertilization.

Testicular problems

There are plenty of things that can can go wrong with the testicles, and rather than provide pages of information here, I have made brief notes, and provided links in the table below which may be helpful if you want to follow any of these items up in more detail. I find the subject of testosterone insensitivity and intersex conditions especially interesting to me, so there are several excellent websites and references on that subject.

Torsion of the testicle

Perhaps the most common problem is torsion of a testicle, when it spins around on the spermatic cord, which carries the spermatic artery, and cuts off its own blood supply. This is a medical emergency, and usually needs surgery within four hours if the testicle is to be saved. Sometimes the docs will stitch it in place so the torsion doesn't happen again. I find that my testicles sometimes seem to be upside down or generally not sitting quite right in my scrotum, but they have never twisted. There is a personal account of testicular torsion in the table of links below. It seems to have been a painful experience. As the testicles' blood supply is reduced, they gradually turn red, then purple and eventually blue. The pain is excruciating, and medical help is essential.


Next, there are infections of the epididymis and seminal vesicles. They are usually the result of infections spreading back from the bladder or up the urethra. The epididymis is a highly coiled structure which is situated on and around the top part of each testicle. It serves to transport sperm, acts as a storage container and allows the sperm to mature on their way to the Vas Deferens. the vast majority of pain in the testicles comes from infections of the epididymis.

Cancer & scrotal self-examination

Testicular cancer is the most common cancer of young men, and ironically it is easily treated if caught early. The recommended way of doing this is for every man to give himself a monthly testicular examination. This can be fun, especially if your partner helps. There is more information on how to do this in the links table.


A Varicoele (Varicocele) is a dilation (enlargement) of the veins that drain the testicle. It feels like a bag of worms inside the scrotum, and is generally much less obvious when a man is lying down than when he is standing. It's present in 15% of the general male population and 40% of men evaluated for infertility. It develops because the valves in the veins taking blood away from the testicle stop working, thereby allowing the blood to pool around the testicle. Testicular injury may occur due this abnormal blood flow, which creates a hostile environment for sperm development. It can be dealt with by an outpatient procedure, although I think it fair to say that the influence of treatment in improving fertility remains controversial. Varicoele is a common result of a blow or kick in the balls, a fact which behoves all athletes to wear appropriate protective gear!

Diseases in other parts of the body which can affect the testicles

Basically any disease which puts the male body under stress will cause the hormonal system to fall out of balance and affect the working of the testicles. Extreme physical exertion will also cause a marked drop in testosterone production, a fact which athletes in advanced training may find quite challenging, since testosterone is necessary for maintenance of the correct bone density in men. Anorexia, as you might guess, severely disturbs testosterone production, and so, oddly, does obesity.

Early male menopause, which amounts to a failure of testicular activity, has been blamed in part on heavy drinking, and it is a fact that alcohol is directly toxic and rather damaging to the testes. Hepatitis and diabetes also have profound effects on testicular activity, especially production of testosterone. Finally, chemotherapy for cancer can be especially disruptive to the testes, and they are also exceptionally sensitive to ionizing radiation. They are, in short, very delicate organs, which are probably not treated with enough respect by many of their owners!

Testicular damage due to overheating - tight underpants, retained testicles, and disposable diapers (nappies)

Brief periods of elevated temperature can markedly reduce sperm production, a fact which has produced scare stories about tight briefs reducing fertility and disposable nappies endangering a boy's future reproductive career. The position is still not resolved, although it seems certain that wearing briefs rather than boxers will not render you childless! Even so, one authority on the male menopause recommends the looser underwear as part of his treatment strategy for menopausal males. The issue of disposable diapers may be less clear, however.

Over the last fifty years, some authorities claim there has been a drop in both quality and number of sperm in the average man. This is a controversial claim, but those who support it have leveled the finger of blame at all kinds of things, environmental pollutants being highest on the list, with the increase in temperature of the scrotum caused by such things as tight fitting underwear, sedentary jobs, and increased sauna usage, following close behind.

According to a team of German scientists writing in the journal Archives of Childhood Disease, a new culprit may have emerged for both the worrying drop in sperm count and the increase in testicular cancer among young men: plastic-lined disposable nappies (diapers).

The authors, who work at the department of pediatrics at The University of Kiel, suggested that a long term rise in temperature of the scrotum caused by plastic-lined disposable nappies might damage the development of sperm. They therefore set out to investigate whether plastic lined nappies had any impact on scrotal temperature, and hence perhaps on decreased fertility, by using tiny thermometers placed inside babies' and toddlers' nappies. The children wore disposable nappies for one period of twenty four hours, then cotton nappies for a second period. The thermometers measured scrotal temperature every thirty seconds.

The results seemed clear: the disposable nappies raised scrotal temperatures by up to one degree centigrade compared to the cotton nappies, while the rectal temperature of babies wearing either type of nappy was the same. Clearly, the scrotum cannot cool itself as it normally would if a child wears disposable nappies, though the authors only claim this may be one factor in declining fertility. Perhaps not surprisingly, the Absorbent Hygiene Products Manufacturers' Association denied any link at all, saying the conclusions were irresponsible and the study critically flawed, since fertility began to fall before the second world war, when disposables had not been invented.

Mountain biking, scrotal problems and impotence

A study published in the British medical journal The Lancet, suggests that 96% of keen mountain bikers showed scrotal abnormalities, compared to 16% of non-bikers. Many of the bikers also reported discomfort and tenderness when examined. The problem appears to be constant vibration and shocks from the rough terrain. The author of the report suggested that bikers should wear padded shorts and use ergonomically designed saddles. But the bikers may be exposing them selves to other problems as well as scrotal and testicular damage: erection problems and impotence are a major side effect of prolonged biking, too. Follow this reference up in the table below.

Primary and secondary hypogonadism

The failure of the testes to produce an appropriate level of testosterone for the body to which they are attached is called primary hypogonadism. The failure of the hormonal mechanisms that control the testes is called secondary hypogonadism.

A variety of testosterone preparations are available that will substitute, with greater or lesser degrees of success, for a man's own testosterone. These include oral preparations, bi- or tri-weekly injected esters of testosterone, skin patches, and long lasting pellets implanted under the skin. There is more information about all of these on the male menopause page of this website and there are plenty of references in the table below.

Anorchia and maldescended or undescended testicles

Anorchia is the absence at birth of one or both testicles. Both are absent in about 1 in 20,000 males; one is absent in about 1 in 5,000 births. One testis is actually enough for a male to develop normally, so that in most cases treatment would not be given, beyond checking that no remnants of testicular tissue were trapped inside the body.

But for the male unfortunate enough to be born without either testicle, testosterone treatment from puberty onwards is necessary for him to live a normal life. For such a boy, the degree of maleness of his penis and other internal reproductive organs would depend on the stage of development at which he lost his testes (which, by the way, may be caused by testicular torsion in the uterus).

Although this is a different condition to the genetic males who appear female at birth through a mechanism of androgen resistance (a term explained lower down this page), there may a similar decision to be made about gender assignment at birth. If the boy has a very small and abnormal penis and no internal male reproductive organs, a combination of surgery and estrogen therapy may be used to reassign him as female. This strategy has led to a lot of very unhappy people.

The testes are generally in the scrotum when a male baby is born, but their journey can be interrupted so that a baby is born with them incompletely descended. The origin of these cases is often unclear, but they tend to be linked to more serious conditions associated with hormonal problems of one sort or another like Klinefelter's syndrome. In other cases they are of what the medics call multi-factorial origin, and are put down to hormonal, genetic or structural abnormalities in the baby's development.

The problem is that they may lead to impaired fertility: one clinic reports that amongst the general male population, infertility runs at around 0.5%, while among men with a treated or still existing maldescended testicle, the rate is nearer 8%. The longer a baby boy's undescended testicles are left untreated, the more likely he is to have fertility problems. And unfortunately the risk of a tumor is several times higher in men with a history of maldescended testicles than in the general population.

Very rarely indeed will a baby boy develop three testes; one case is documented in the medical literature where a vasectomy on two testicles didn't work and the still-fertile third one was only found only when the man concerned continued producing offspring (no doubt much to everyone's surprise).

The report does not explain how the doctors and, indeed, the man himself, had missed finding his third ball........ In another amusing case, in 1540 Count Philip of Hes was given permission by Martin Luther to take a second wife - at the same time as his first, that is - on the grounds that he had three testicles. Hmm.

Retractile testicles - normally during sex, and inconveniently at random

A problem sent in by a reader: Sometimes my scrotum will retract to the point of pain. It seems to happen when I am working (hard), a lot of movement or sometimes for no reason at all. I am 30 years old and in good health. This has been happening for years but seems to be happening more and more. Most of the reading material I have read states that this happens with a quick change of temperature or longer periods of being in the cold, but this does not seem to be a major factor. Can you please shed some light on this subject for me?

An answer: Well, a degree of contraction in conditions of cold or fear and at the point of ejaculation is quite normal, and is called the cremasteric reflex. It is caused by the muscles of the scrotum retracting and drawing the testicles up into what becomes a tightly contracted, wrinkled scrotum. I have had several queries from guys asking exactly why they should have testicles that retract this much - as you say, sometimes to the point of pain.

The answer seems to be that it is just another example of individual variation. However, some guys actually find that under these conditions of cold, fear or sexual excitement, their testicles retract right into their body. Many of the guys who have written to me about this seem really pissed off about it. They have testicles that have spent much of their lives tucked away out of sight! It also seems to happen a lot when they are slightly anxious.

Medically the condition is known as retractile testicles, and it refers to a situation where the testes do not remain outside the body all the time, but retract into the inguinal canal (which is the passage down which they came when they descended into their scrotum as a baby). Most men, even when their scrotum is tightly contracted in conditions of fear or cold, do not have their testicles disappearing altogether into their body!

Even so, retractile testicles are not an uncommon condition in the male population, and they rarely have any pathological significance - at least, as far as is known. Most medics would say that apart from the fact that their owners don't like it, it isn't a big problem. On the other hand, one andrologist says it may cause lowered efficiency of sperm and testosterone production over a long period of time (obviously the testicles are meant to be cool, that's why they are outside the body in the first place).

Question: I was diagnosed a few years ago with a condition called retractile testicles. At the time my doctor told me I would just have to live with it. I've tried but find it very uncomfortable when I do any sporting activities as my testicles retract. Is their anything I can do to correct this uncomfortable condition?

Answer: Retractile testicles are very common and it merely means that although your testicles hang normally in your scrotum most of the time, they are pulled up by certain muscles into the groin area in certain circumstances.

Swimming, especially in cool water, will almost always cause this, as the natural tendency of the muscles in the skin surrounding the scrotum is to contract in the cold. The cremaster muscle pulls the testicle upwards and in some men into the inguinal canal that lies just above and behind the crease at the top of the leg where it joins with the abdomen.

This happens too when you are nervous or anxious as a result of stress hormones, as well as during sporting activities. During physical exertion blood flow is diverted to the exercising muscles and away from the genitalia. Again the testicles are pulled up as a result.

During sport, the scrotum contracts to protect the testicles from harm, and in fact, retractile testicles have a protective value in contact sports for this reason. Professional sumo wrestlers in Japan actually massage their testicles into their inguinal canals deliberately so they do not become injured during wrestling.

Testicles normally and naturally retract during sex, especially prior to ejaculation. Whilst your condition is normal, it can sometimes be uncomfortable. You will find that wearing warmer under clothes will definitely help as your scrotum will relax just as it does in a hot bath. You could also wear a sporting jock strap rather than ordinary pants, as these are more comfortable to wear with your condition.

Retractile testicles in a baby

From the Medhelp forum (click here to go to this excellent medical forum):

Question: I have been to a pediatric urologist about my 14 month-old's retractile testes. After a quick exam, he said the protocol was not to treat but to re-check every year until puberty, at which time he would need surgery if they were not permanently descended. I still worry about infertility...if the testes are hardly ever descended, as my sons are, how can the heat inside the body cavity not be an issue?

Also, I read that some urologists differentiate between gliding and retractile testes, with a gliding testicle being one that glides right back up after being brought into the scrotum and a retractile being one that stays down for a few seconds. The article said that gliding testes should be treated with surgery. This was a Canadian document. Are American physicians under-treating retractile testes? Am I concerned over nothing?

Answer: Undescended testicles are called “cryptorchid”. The incidence of cryptorchidism is approximately 2-4 percent in all newborn boys. The incidence is higher in boys who are born premature. In such individuals, the testicle can be found anywhere in the inguinal canal, and possibly up in the abdomen (failing to have descended or partially descended). The testicles in cryptorchid boys can not be brought down to the scrotum, or may be brought down manually during examination under tension.

However, in normal boys with retractile testicles, the testicle can be brought down to the scrotum, but may retract again secondary to the cremasteric reflex. The cremasteric reflex results in elevation of the testicle into the upper scrotal or intracanicular position by contraction of the cremasteric muscles which are stimulated through this reflex. Retractile testicles are essentially testicles that can be brought down to the normal scrotal position, and stay down, until they are stimulated to retract again by a hyperreflexic cremasteric reflex.

Retractile testicles are essentially considered to be descended and therefore normal. It would be difficult to say whether physicians in the U.S. are under-treating retractile testicles or not, since they are by definition considered retractile and therefore normal. Either your son has undescended testicles which would require surgical intervention at this time, or they are normal (or retractile) and only require observation.

If a testicle is normal (or retractile), then under-treatment would not be an issue. When your son’s urologist favored watching every year to see if the testicles descend, was there a question of whether they are undescended or not? If so, then your concerns may be warranted. However, if he/she and you are sure that they are descended (retractile or not), then there should not be a concern for future testicular cancer, etc. I hope this sheds some light on your situation.


Vasectomy has an interesting history, not all of which is positive: it was used by the Third Reich for eugenic controls, a fact which some authors claim has contributed to its unpopularity in some countries and cultures. However, it is also possible that it is unpopular because it is seen as irreversible: severing the tubes that take sperm from the testes to the penis does sound like a fairly radical method of birth control, after all.

It might therefore be considered only really suitable for stable relationships where a couple's family is complete. Anyway, whatever, in the USA, 25% of couples rely on vasectomy or the female equivalent of tubal ligation for contraception, though blacks (by which I imagine the researchers mean black men) clearly prefer female sterilization to male sterilization; among whites, men and women go under the knife in roughly equal numbers.

No special social or medical requirements exist for a vasectomy, though many physicians will not perform it unless the man has met certain preconditions: for example, unless he has a stable relationship and a certain number of children, or perhaps unless the written consent of the partner is provided. But these are individual issues for the doctor, and as long as the patient is fully informed about the operation, then most doctors will operate fairly readily.

The object of the surgery is to sever or occlude the spermatic ducts so that the sperm are prevented from leaving the male body. The procedure is simple: the spermatic cords are anesthetized, the ejaculatory duct is located beneath the scrotal skin and clamped, the scrotum is opened with a scalpel with a cut of about 1cm, the vas deferens is cut, a piece about 1 cm long is removed, and the ends are sealed and tied off. the skin is then sutured, and the procedure repeated on the other side.

(A new, no scalpel technique is described by one clinic whose link you can click on in the table below.)

The effectiveness of vasectomy as a contraceptive is very high - it is reported to be 99% successful or more in producing aspermatic semen. (Several tests are necessary to ensure that sperm are fully discharged from the portion of the testicles above the severed duct.) And short term operative complications are very rare, though they do occur: infection or bleeding into the scrotum are the most common, so undertaking the procedure with a competent medical facility on hand is important.

However, some authorities suggest that there may be more long term consequences than have previously been acknowledged. The most common is sperm granuloma, described here.

From an Internet Medical Forum:

I am a 46 year old male, and am having pain from small pea sized semi-hard lump at the end of the vas which was cut during vasectomy.

Commonly, a painful mass at the site of a vasectomy is a sperm granuloma. These are usually harmless, but on occasion can be painful. A course of antibiotics can alleviate the symptoms. But, rarely the pain will persist and excision of the granuloma will be necessary. Thomas Stellato, MD

The lump you describe is most likely a sperm granuloma, which is a low-grade leakage of sperm from the cut end of the vas deferens. This is a nor
mal finding. It is completely benign and portends no later complication or bad sequela. In fact, it is often a good finding in cases where a person might seek a vasectomy reversal, as it indicates a higher likelihood of successful vasectomy reversal. Aaron Spitz, MD

There are a number of other effects described by men who have had a vasectomy, including feelings of heaviness, fullness or pain, which are usually temporary.

As always, one must qualify this assertion, for there are some reports on the net (see links below) from men who have suffered prolonged pain from vasectomies, though whether this is a result of poor surgical technique is unclear. Up to 70% of men who are vasectomised form antibodies to their own sperm, which suggest that leakage of sperm is occurring into the soft tissues or bloodstream around the cut in the vas deferens.

There are few medical comments on this, but various studies have tried to prove or disprove links between vasectomy and other diseases including arteriosclerosis, diabetes, prostate cancer and immunological problems.

The results to date have been inconclusive because most studies have looked retrospectively at patient history - and the results of modern, well controlled, current studies will not be available for some time to come. I strongly suggest that you look at the links table below and read the relevant references before you decide whether or not vasectomy is the method of contraception you want to use.

Is vasectomy reversible?

A good question, indeed. Partners die, children (Heaven forbid) die, men and women remarry, and circumstances change. And often the desire to have children goes with these changes. If a man has been vasectomised, and has not taken the (expensive) precaution of freezing some of his own sperm in cryogenic storage, will he be able to father children? In other words, is vasectomy reversible?

The answer is it depends on the competence of the surgeon and the degree of destruction of the vas deferens that accompanied the original surgery, but success rates of 90 % are achieved by those surgeons most experienced at rejoining the severed ends of the vas deferens. And even if this fails, it is possible to extract sperm directly from the testis. But......don't count on it.


Testosterone is a hormone that has had a bad press: it has been blamed for a lot of the trouble in the world, if only because it seems to have a connection with aggression and violence and risk taking behavior. And of course, this kind of male behavior can be aggressive and threatening, especially to women and children. But this seems like blaming a dog for barking: that is what testosterone does - it makes men male.

Let me add at once I don't mean to imply men are compelled to take part in aggressive and risk taking behavior - to claim that would be to demean our human ability to control our behavior and make choices in life. But clearly men and women are different psychologically, and as any parent would probably readily agree, so are boys and girls.

Ah, I hear you say, boys don't have testosterone till they reach puberty - true, but they have certainly been exposed to it in the uterus, from their budding testicular tissue, which produces the testosterone responsible for the development of their penis and testicles, and, furthermore, their brains have been made male by it.

Testosterone is the main hormone produced by the testicles, along with 5 alpha dihydrotestosterone, androstenedione, and a number of others. The androstenedione is important in the production of estrogen, or, more accurately, estradiol, in the male body. Although this has a number of important effects in male physiology (for example, it is crucial in the mechanism of bone growth, or, rather, the cessation of bone growth, at puberty), it can also be very unhelpful - see the page on the andropause for more information.

Testosterone is transported around the body bound to a protein called Sex Hormone Binding Globulin, or SHBG. At any one time in the male body only 2 % of the testosterone in the bloodstream is actually free of SHBG, and it is only this free component that is biologically active.

The increase in SHBG and the consequent decrease in free testosterone appears to be a major factor - and not one widely recognised - in why men may appear to have "normal" levels of testosterone but suffer menopausal or andropausal symptoms when they're past 40 years of age. This is explained in more detail on the andropause page of this website, where there are also plenty of good books recommended which will give you a clear picture of where conventional medical thinking may have gone wrong on the subject of the andropausal male.

In male tissues, testosterone is metabolized into two other molecules which also have important hormonal effects in men. As mentioned above, one is estradiol, the other is 5alpha-dihydrotestosterone (DHT). At the cellular level, DHT is the compound responsible for male differentiation and development of the developing fetus - and so, if, due to a genetic mutation, the tissues of a male baby have difficulty converting testosterone into DHT, he may appear to be female to a greater or lesser degree, with incomplete virilization.

Another reason that male babies - I mean genetically male, ones with an XY chromosome - may not develop full masculine features is that the mechanism by which their cells are influenced by DHT or testosterone does not work as efficiently as it should; again the process of male differentiation will be incomplete to a greater or lesser degree. It is a peculiar fact that all embryos will develop female characteristics in the effective absence of the male hormone, but it is a fact nonetheless.

There are several different degrees of unresponsiveness to testosterone in the male body, ranging from 1 to 7, where 7 indicates complete feminization, known as testicular feminization. These are genetically male individuals, who have no responsiveness to the androgens produced by their tissues and are to all intents and purposes female, and often very attractive females at that.

Testicular feminization & intersexuality

Androgen resistance is defined as a state where hormones are present in sufficient quantities but do not have the expected effects on the target organs. This is due to deficiencies in the androgen receptor on the individual cells of the body, which constitutes the mechanism by which hormone flowing around the body impacts upon the cells. The original cause of the androgen resistance is a well-defined genetic abnormality of greater or lesser severity. I have included some references below if you want to follow up on the subject, but what this amounts to is a problematic condition for doctor and patient alike.

Complete testicular feminization is always accompanied by a female psychosexual orientation: not surprisingly, perhaps, as the external genitalia appear female, although the vagina is often rather short, and the individual will have been assumed by all to be a female from birth.

The diagnosis may be made when a "girl" is treated for the absence of menstrual periods at puberty, or for inguinal hernias earlier in life. Internally, there is neither a uterus nor Fallopian tubes, although there may be gonads made up of testicular tissue, which are incapable of producing sperm and often develop tumors.

Estrogens in the body of such a girl, whether administered as part of a medical regime, or produced by the abnormal tissues of her gonads, will produce a female body form, although she will have no axillary or pubic hair, which is dependent on the hormone testosterone in both male and female individuals.

In the past, when a woman has been diagnosed as a testicular feminization individual, the diagnosis has often not been conveyed to her, on the grounds of potential damage to her self-image as a woman. This may be a reasonable approach for some individuals, but to apply it as blanket approach to all cases surely represented the supreme level of medical arrogance, in denying the patient the experience of her own existence.

How such a patient should be told is still controversial, and whatever method is adopted, one thing's for sure: it would be a remarkable individual indeed who did not need help from a trained counselor to readjust their self-image.

Partial androgen insensitivity & incomplete masculinization

An orderly classification of male deficiency into neat categories, starting with the complete androgen resistance that results in testicular feminization, and going across a spectrum to normal maleness is too simplistic, both for the medical profession and for the person concerned.

What in essence androgen resistance amounts to is that a person may show greater or lesser male characteristics, and, regardless of what the medical profession may think, everyone's primary concern should be to bring the child up with strong self-esteem regardless of their physical appearance. I must say that there are violently opposing views about how this can be done.

The medical profession have traditionally taken the view that a child's sex must be identified as closely as possible to the most realistic condition, and that the child's carers must then never deviate form that position, which will be supported by surgery if necessary.

Thus, often intersex "girls" with oversize clitorises (a product of their sensitivity to androgens in the uterus) have often been subject to clitoral reduction or removal, sometimes removing all their sexual feeling and their ability to have orgasms. Similarly, boys with small and very hypospadic penises have been subjected to repeated surgery (which may be unsuccessful) designed to give them a "normal" penis.

This all seems at the least highly questionable, and a vociferous body of opinion has emerged, noticeably in America, that advocates leaving any surgery until an intersex person is able to decide for themselves what gender they wish to identify as, and whether or not they wish surgery to take place on their genitals to modify the appearance. Often, it seems, their conclusion is that they do not want surgery. I can understand the desire of the medical profession to ease a child's passage through life with a firmly assigned gender identity, but there are very considerable difficulties if the process goes wrong.

In less marked cases of androgen resistance, the external genitalia may resemble either a poorly developed penis or an oversized clitoris; if there is a penis, it may have hypospadias, with the opening as far back as the scrotum; at puberty, pubic and axillary hair may be normal, while hair on the face is much less marked. There may or may not be menstruation or breast development. As the condition swings towards the male end of the spectrum, the child has more recognizably male genitals, but the penis may be small and undeveloped.

These are distressing enough symptoms, but what is much worse are the problems that arise when doctors have assigned a sex to the child - sometimes after rigorous genetic and biochemical testing, sometimes not - and the child has then grown up with the conviction that they belong to the opposite sex. It is biologically quite possible for brain and body to be at odds in this way: all that it needs is for the brain to be more masculinized than the body by whatever testosterone the baby was exposed to in the uterus, or vice versa, and you have a person who will never settle comfortably into their assigned gender. If you wish to research more about this, I have provided references in the table below.

The very mildest form of androgen resistance results in an almost normal male appearance, though perhaps with a small and slightly unusual penis such as mild, coronal hypospadias (though hypospadias may be caused by very mild androgen resistance, it would be a mistake to assume this is always the cause of hypospadias).

I should also point out that a small penis in itself is not a means of identifying androgen resistance: a small penis is not uncommon, and it needs to be accompanied by lack of androgen dependent hair (eg on the face), lack of pubertal development, and perhaps a psychological sense of incomplete maleness, and investigation into fertility and endocrinological studies before a diagnosis can be made. And what then, anyway? If by definition a person is androgen resistant, supplementary testosterone may be ineffective in virilizing the man concerned. A tricky problem, indeed.

A last word on testicle size

Biologists seek clues in may places to aid their understanding of evolution. One of the areas that has attracted their attention is the differences in relative size of testicles and penis between chimps, gorillas and man, all of which are closely related species. In essence, it appears that both testicle size and levels of sperm production are related to the level of female promiscuity in a society. For example, gorillas have both small penises and testicles, and although the males are polygamous, the females are monogamous.

By contrast, in chimpanzees, each female is impregnated by many males, and the prevailing theory is that those males with larger testicles have an advantage because they will be able to produce and ejaculate more sperm, thereby winning the so-called sperm wars that occur in the female's vagina; the prize being the opportunity to fertilize her eggs. In a way this begs the question of why societies evolved different reproductive strategies in the first place - why is the gorilla society dominated by a single silver backed male, while chimps, although still hierarchical, with the alpha and beta males ruling the roost, are more polygamous?

That however is a separate question. If the graph of female polygamy versus male testicle size is drawn, the position of man on the graph is somewhere between the chimp and the ape, thereby giving a spurious validation to the conclusion that most of us have probably reached about humankind's sexual behaviour anyway - that we are mildly polygamous as a species. Here is an extract from the article that put forward the idea :

" the chimpanzee, several males mate frequently with the estrous females, so that each male has to deposit enough sperm to compete with the presence of sperm form other males. For the chimpanzee, therefore, we hypothesize that selection will favor the male that can deposit the largest number of sperm; thus the volume of spermatogenic tissue and hence the testis size is far greater in the chimpanzee than in the gorilla or orangutan. If this is correct, it implies that primates in which more than one male mates with each estrous female should have larger testes relative to their body weight than those which single-male breeding systems.

We have tested this prediction across a wide range of primates, and the results support the hypothesis. The relative size of testes may, therefore, provide a valuable clue to the breeding system of a primate species." Harcourt AH, et al., 1981. Testis weight body weight and breeding system in primates. Nature 293, p. 55

And again:

"'s testicles are medium-sized - considerably bigger than a gorilla's. Like a chimpanzee's, human testicles are housed in a scrotum that hangs outside the body where it keeps the sperm that have already been produced cool, therefore increasing their shelf life, as it were. This is all evidence of sperm competition in man.

But human testicles are not nearly as large as those of chimps, and there is some tentative evidence that they are not operating on full power (that is, they might once have been bigger in our ancestors): sperm production per gram of tissue is unusually low in man. All in all, it seems fair to conclude that women are not highly promiscuous, which is what we expected to find." Ridley, MW. 1993. The Red Queen, p 220.

There are a number of problems with this theory, though, one of which is that testicle size in some races are much smaller than in others. All men are not, it would seem, created equal:

"Although measurements of testis size by orchidometry in living subjects are difficult to standardize, they suggest smaller testes in Japanese and Korean men than in Caucasians. Weighing at autopsy is more accurate and showed that the size was twofold lower in two Chinese samples compared with a Danish sample. Differences in body size make only a slight contribution to these values." Diamond, JM. 1986. Variation in human testis size. Nature 320, p. 488.

This highly amusing field of science has, inevitably, also been applied to the size of the male penis. Sadly, though, the apparent facts about penis size don't fit the testicle size theory, for although gorillas do have a very small penis, the biggest tool of all is owned not by the chimp (he of the enormous balls, you may recall), but by mankind.

Why would we need a proportionately big penis while having relatively moderate sized testicles? If the sperm war theory is correct, you could see how a longer penis might deliver sperm nearer to the egg and therefore confer an advantage over other males on its owner - but if this were true for humans, it should also be true for the chimp - and it appears not to be. Does this mean that there was a separate pressure on the evolution of penis size in man? Who knows? And if there were, what could it have been? Or is this just pseudo-science of the least valuable kind? Well, it may be, but it is fun, isn't it?


1 Testicular problems


Varicocele info from Mayo Clinic

A varicocele is a dilation (enlargement) of the veins that drain the testicle. It feels like a bag of worms inside the scrotum, and can reduce fertility.

The Dangers of (Mountain) Biking: reduced fertility and loss of erections!

There is plenty of evidence that the pressure of the saddle on the perineum can contribute to erection problems in later life, as it damages the penile artery. You can read more about this here. You can always use a padded, ergonomically designed saddle or a pair of padded shorts. Whatever, if you feel tingling or unusual sensations in your nether region, stop biking!



Granuloma & testicular pain

Vasectomy is, in theory, a simple process of cutting the Vas Deferens that carry sperm from the testicles to the penis. However, before you take the plunge, you might want to read the articles linked on the left.
It had to happen - a whole, real-life vasectomy in pictures. What can I say! Commentary by the guy whose tubes are being snipped.


Testicular Cancer Resource Center

Testicular cancer is the most common cancer of young men, but happily it is easily treated if caught early. The recommended way of doing this is for every man to give himself a monthly testicular examination. This can be fun, especially if your partner helps.

Pelvic/testicular pain

This is one possible explanation of testicular pain that cannot be diagnosed and in fact may be misdiagnosed as epididymitis.

More information on problems of the testicles, including spermatocele

Testicular anatomy, problems, and other information. Includes a fascinating account of how the testicles descend normally and why they sometimes fail to do so. Excellent.

Retractile and undescended testicles in babies and young boys - from Medhelp

Information from the questions and answers section of Medhelp, with a good summary of the problem, how it can be dealt with, and why it should be treated.
HYPOGONADISM Includes specific recommendations for determining the most effective methods of diagnosing and treating hypogonadism in adult male patients. Target populations include the following: (1) males with primary testicular failure requiring testosterone replacement (hypergonadotropic hypogonadism); (2) males with gonadotropin deficiency or dysfunction who may have received testosterone replacement therapy or treatment for infertility (hypogonadotropic hypogonadism); and (3) aging men with symptoms relating to testosterone deficiency who could benefit from replacement therapy.

Chlamydia and testicular infection - epididymitis

The first link is a bit technical but informative. The second deals with Chlamydia, which is one cause of testicular infection. It can have nasty long term consequences. If you still want more information, go to Search Engine Google and type in epididymitis. You'll get loads of informative links.
Testicular torsion A journalist's account of it happening to him!

2 General information

Explains the isssue of low sperm count. Loads of reasons why you might not be getting her pregnant.
Semen analysis From the point of view of fertility (or, rather, infertility).

For more testosterone information, please see the andropause page of this site.

3 Vasectomy

The no-scalpel vasectomy Benefits and problems.

Granuloma & testicular pain

Vasectomy is, in theory, a simple process of cutting the Vas Deferens that carry sperm from the testicles to the penis. However, before you take the plunge, you might want to read the articles linked on the left.

4 Birth problems, sexual development issues, intersexuality, androgen insensitivity

Intersex Society of North America Another great organization, supportive and necessary for all struggling with sexual determination and gender identity
UK Intersex Society This is the introduction page of the United Kingdom Intersex Society (UKIA), an education, advocacy, campaigning and support organization which works on behalf of intersex people.
Androgen Insensitivity Syndrome (AIS) Informative and useful.

5 The "odder" stuff on the testicles, penis and semen

Penis and testicle size Collection of pieces on the evolutionary pressures affecting testicle and penis size.
Large testicles linked to adultery? It's that evolution thing again.
The Upsuck Theory of female orgasm It is a fact that women who orgasm as their man ejaculates get pregnant quicker. Could the female orgasm be a means to draw semen up into the uterus?