Figure 1 Formation of the penis or the vagina
“Snips and snails and puppy dogs’ tails, that’s what little boys are made of.” So goes the nursery rhyme, but it’s a lot more complicated than that. Boys are made of many parts, the most obvious being the penis. How boys end up with penises and girls end up with vaginas is the result of genes, hormones, and the environment. We all start out as girls, and then for some, a penis forms and other remodeling happens. Understanding how the penis develops allows us to understand why some boys are born with penises that are abnormal. In some cases, rebalancing hormones can help restore the penis to a more normal state. Surgical correction can be challenging, and sometimes reconstructing the child as a female is more feasible.
There is a particular center in the brain that is critical for gender self-identity. This area usually develops differently in boy brains than it does in girl brains, but not always. When an exception happens, a man will literally feel like a woman trapped in a man’s body and vice versa—not by choice, but by biology. Understanding the brain’s influence on gender helps us to better understand why infant gender reassignment can be fraught with frustration for a person as he or she grows up. It also helps us understand why some boys are born who will not want a penis and why some girls are born who really will. Doctors and society have come a long way in our ability to help these patients through a combination of hormone therapy, complex surgery, and enlightened understanding.
A baby human’s genitals start to form during the 7th to 9th week after conception. Up until then, the fetus has been neither male nor female. The fetus has what is called a “genital bud,” which is a spin-off of the tail bud that in humans disappears and in other animals goes on to make a tail. If the fetus is male, the Y chromosome allows the formation of testicles, which then release testosterone. Testosterone makes the developing vagina fuse in the middle and become a penis. What otherwise would have become the labia majora become the two halves of the scrotum. What would have been the clitoris enlarges to become the head of the penis, and the chambers that fill with blood to make the penis erect grow larger than the much smaller versions that would be attached to the clitoris in a girl. The urethra lengthens and tunnels up through the head of the penis. From the 3rd month of pregnancy until near-birth, the testicles will slowly work their way from inside the abdomen, down into the scrotum. If the fetus is female, she forms ovaries instead. Without testosterone, this all wraps up by the 13th or 14th week. At the same time, other internal features of both sexes develop, such as the uterus and ovaries or the prostate and seminal vesicles. The testicles release a special chemical called Mullerian inhibiting substance that prevents the uterus and fallopian tubes from forming in males.
Things can go wrong along the way. Let’s start at the tip. The foreskin grows from just below the head of the penis and covers it up completely, then the tip of the foreskin disintegrates, leaving it as a sleeve instead of a sock. If it doesn’t disintegrate enough, the opening of the foreskin will be too tight. Rarely, some boys are born with no foreskin or with very little, which results in their being born with a circumcision, more or less. Also rare is excess foreskin, which can be a trickier situation because it can trap urine and is difficult to keep clean. A circumcision can help, but it must be done carefully because the extra foreskin is not always a simple tube of skin. What seems to be a simple cut can result in a skin doily.1
A more common condition is hypospadias, when the urethra does not form all the way to the tip of the penis. It may end at the base of the scrotum, midway up the shaft, or just below the head. When the urethra is not completely formed, neither is the foreskin: It will look more like a hoodie than a turtleneck. The cause is not completely understood, but hypospadias is more common in premature births and when the mother suffers from the flu, high blood pressure, or diabetes early on in her pregnancy. Also, there seems to be a slight increase among babies conceived with in vitro fertilization. There is also evidence that many chemicals we are exposed to can act like estrogen and may interfere with normal male development. These chemicals are called “endocrine disrupters” and they are everywhere, from plastic bottles to toys to medications to makeup.2 Surgical correction of hypospadias is usually performed during infancy. The foreskin is used to lengthen the urethra, so it must not be removed with a circumcision before the urethra is repaired! For repairs where the distance from the urethra to the tip of the penis is substantial, skin from other areas may be used to make a new passageway.3
Rarely, problems may arise with the development of the shaft or head of the penis. These structures can make like a blackjack hand and double down, split, or fold.
Figure 1 Formation of the penis or the vagina
Figure 2 Hypospadias: different degrees of severity
Diphallia is a condition in which the genitals of the fetus get duplicated, resulting in two penises, two rectums, and two anuses. Sometimes the doubling is incomplete and one of the penises is much smaller, like a T-rex arm. Two heads are not better than one. Urethras or rectums can end up completely blocked, creating a medical emergency. This condition can be corrected with surgery, in which one of the “twins” is removed.
Sometimes the penis doesn’t double down, but rather splits. When the two halves of the penis shaft don’t fuse properly, the penis chambers and the head end up somewhat separated by a long, deep groove. As a result, the urethra opens up way back towards the base of the penis, on the top side. This condition is called epispadias. Often there is urine leakage because the bladder sphincter doesn’t close normally. With epispadias, the penis curves upward, which can make aiming for the bowl a challenge.4 Commonly, the lower pelvic bones don’t come together, nor do the two sides of the abdominal wall or the two sides of the bladder. The unfortunate child is born with the penis completely split apart and the bladder open and exposed. Fortunately, this condition can be treated by a team of talented pediatric surgeons. The two halves of everything that didn’t come together are surgically brought together, from the bones to the boner.
Figure 3 Epispadias and bladder extrophy
A very rare situation is that of a double urethra, and even more rare is a double bladder. In these cases, there is one normal urethra and then a second that may end short on the underside of the shaft, but without any curvature to the penis.
Sometimes the developing penis just bows out. Aphallia, meaning “no penis,” is a rare condition that usually occurs with other life-threatening birth defects. It happens because the genital bulge never properly forms in the fetus. Rarely, a boy may be born without a penis but with no other severe abnormalities. He will have testicles, but his urethra will typically open near his anus. Another reason a baby boy may end up with no penis is from a severe circumcision complication. Surgical reconstruction of a penis in a male infant is extremely difficult or even impossible, while creation of a vagina is fairly straightforward and usually successful. When a baby boy’s penis is absent or severely injured, the parents and medical team may choose to surgically reconstruct the genitals as female and, with the aid of hormone supplements, raise the child as a female.
Sometimes female infants may be born with what appears to be a penis due to increased growth of the clitoris due to excess levels of testosterone produced by overactive adrenal glands. The adrenal glands sit on top of the kidney and normally produce several hormones that regulate various body functions. Excess testosterone will stimulate the clitoris of the female fetus to become abnormally enlarged and the vagina to close in the middle, so the baby girl may appear to have a penis. In less severe forms, the clitoris is enlarged and the labia may be partially fused together, making the vaginal opening smaller than usual. These babies have normal internal female organs and, in more severe cases, they may undergo surgery to reduce the size of the clitoris and open up the vagina. They usually also suffer from severe electrolyte imbalances, which are also due to the abnormal adrenal glands, so it’s critical to recognize that the abnormal genitals may be due to this more serious medical condition.
Too little male hormone can cause a genetic male to be born with female genitals. Androgen insensitivity syndrome occurs when the male fetus has abnormal testosterone receptors throughout his body. Even though the fetus is genetically male, the testosterone just bounces off the cells, which lack testosterone receptors. As a result, the child’s genitals don’t develop into a penis. The child is born with a vagina but it is short, and there are no female internal organs such as a uterus, ovaries, or fallopian tubes. The testicles are up in the abdomen since there is no scrotum for them to drop into. Some of the testosterone is converted into estrogen, so eventually these individuals develop femalelike breasts. They may undergo surgery to enlarge the size of their vagina and remove the testicles.
Guevedoce, or “penis at twelve,” is a genetic condition well known in the Dominican Republic. One out of every 90 boys gets this nickname because he will actually not develop a penis until age 12. Until then, he will appear female and be raised as such. These boys do not produce an enzyme called 5-alpha reductase, which converts testosterone into dihydrotestosterone. Dihydrotestosterone is like a steroid on steroids. It has a much more potent effect than testosterone on male parts like the penis and prostate and hair growth. These children have testosterone receptors, but without the even more powerful dihydrotestosterone to stimulate their penis development, they are born with female-appearing genitals. When puberty comes around, at about age 12, the child gets a surge of testosterone from his testicles, which is enough to make his penis finally develop fully and voilà—penis at 12! This gives a new meaning to “coming of age.” In a society where this is a common condition, these guys then go on to live normal lives as men, though their facial hair is a bit sparse and their prostates are a bit smaller.
Much more common than being born with no penis is being born with a hidden or buried penis. This means the only part of the penis sticking out above the scrotum is the foreskin. The shaft and head of the penis are trapped underneath the fatty tissue right over the pubic bone. Normally the shaft of the penis is surrounded by a fine layer of tissue that is a soft, surprisingly stretchy combination of fat and collagen fibers. If you are a “grower,” you have an up close and personal appreciation of this elastic tissue. In the case of buried penis, that layer of fat and fibrous tissue is very disorganized and loses its elasticity. This keeps the penis shaft held back under the fat pad that surrounds it. The hidden penis will persist into adulthood. The remedy is usually surgery to release the tissue that won’t stretch and then possibly liposuction or additional surgery to cut away the fat pad around the penis. In these cases the penis is not abnormally small, it is just hidden from view, waiting for its day in the sun. Most guys sporting buried treasure can blame it on being obese. When you add diabetes to the mix, the circulation suffers and the foreskin can shrink and close up, aggravating the appearance of a hidden penis.
There are also a variety of abnormal variations of the scrotum and where it attaches to the penis. For example, the scrotum can attach to the midshaft or even the end of the shaft of the penis, giving the flaccid penis a webbed appearance and making it appear small. The erection, however, is completely normal in size.
Figure 4 Hidden penis
Figure 5 Webbed penis
Sometimes the penis is truly smaller than normal. The criterion for micropenis is a soft but stretched penis that is 2.5 standard deviations below the average. What this means for a newborn is a stretched penis shorter than 1.9 cm. The sizes can vary slightly with ethnicity (see Table 1).
| AGE | MEAN CM ± SD | MEAN * SD |
| Newborn 30-week gestation | 2.5 ± 0.4 | 1.5 |
| Newborn 34-week gestation | 3 ± 0.4 | 2.0 |
| 0 to 5 months old | 3.9 ± 0.8 | 1.9 |
| 6 to 12 months old | 4.3 ± 0.8 | 2.3 |
| 1 to 2 years old | 4.7 ± 0.8 | 2.6 |
| 2 to 3 years old | 5.1 ± 0.9 | 2.9 |
| 3 to 4 years old | 5.5 ± 0.9 | 3.3 |
| 4 to 5 years old | 5.7 ± 0.9 | 3.5 |
| 5 to 6 years old | 6 ± 0.9 | 3.8 |
| 6 to 7 years old | 6.1 ± 1.0 | 3.9 |
| 7 to 8 years old | 6.2 ± 1.0 | 3.7 |
| 8 to 9 years old | 6.3 ± 1.0 | 3.8 |
| 9 to 10 years old | 6.3 ± 1.0 | 3.8 |
| 10 to 11 years old | 6.4 ± 1.1 | 3.7 |
| Adult | 13.3 ± 1.6 | 9.3 |
Micropenis happens when the male fetus’s testicles don’t produce enough testosterone during that critical window of penis development early in pregnancy. The testicles don’t make testosterone unless they receive a signal from the brain, so genetic conditions that inhibit brain signals can cause micropenis. In Kallmann syndrome, the part of the brain that signals the testicles is not formed. This often goes hand in hand with a lack of a sense of smell because the “smell” nerves are right next to the part of the brain that secretes the signal, so those nerves don’t form either. In Klinefelter syndrome, the boy has an extra X chromosome, which results in very poor testicle growth and development. In some cases, these boys will not produce adequate testosterone for normal penis growth. A newly increasing cause of micropenis may be environmental toxins, such as pesticides and heavy pollution, which mimic estrogens. Estrogens counteract testosterone during the critical window of penis growth and development early in the pregnancy.5, 6
The treatment of micropenis is to immediately supplement the missing testosterone with topical testosterone gel or injections. The trick is not to give too much, or the bones will stop growing longer and the boy’s height will be stunted. Still, the gains may not be enough, and so one of a variety of surgeries can be performed.
The penis suspensory ligament that anchors the base of the penis shaft to the underside of the pubic bone can be cut, allowing the penis to hang a little longer. The scrotum can also be tapered back. These changes make the penis appear bigger. Another surgical fix is adding tissue flaps around the penis to increase girth. There is very little that can be done surgically to increase the length of the erectile chambers of the penis. In extreme circumstances, a new penis can be developed, but this is rarely done as the vast majority of men with micropenis have fulfilling intimate sexual relationships. For some, the condition can be a source of great distress. It is thought that Napoleon Bonaparte had micropenis, which gives a whole new dimension to the notion of overcompensating.7
On the other end of the spectrum is megalopenis. No, it’s not the newest B-movie craze since Sharknado. As the name suggests, it’s a penis that is bigger than normal by more than 2 standard deviations. In some cases it is due to abnormal genes that cause many other physical, and often mental, defects. In most cases, the cause is too much testosterone stimulating the developing penis, which may be due to a tumor in the testicle overproducing testosterone. This kind of tumor is usually benign. Sometimes there are tumors in other parts of the body that make testosterone or regulate its production. There may be a tumor in the adrenal gland or the pituitary gland, which is the control center for normal testosterone production. Sometimes the testosterone is from medicated gels or ointments that get on the baby from someone else who’s using them. Too much testosterone causes the bones to stop growing too soon and stunts the child’s growth, so the testosterone levels need to get back to normal ASAP. The penis will eventually get back to normal, too. Ah, shrinkage—but in a good way.
Boys will be boys—or maybe not. Hormones, environmental pollutants, and even stress all influence the gender of the developing baby. There is evidence that the brain itself can be either male or female. Some scientists say that there is an area of a boy’s brain that makes him more interested in toys that can be propelled, while a girl’s brain is wired more toward nurturing toys.8 There are also theories about differences in learning styles and strengths—men being hardwired to be better at spatial reasoning, for instance. Of course, societal pressures are at work here as well, so there is a lot yet to understand about brain gender. For boys, the key element that shapes the brain is testosterone. It strengthens some brain connections and pares down others.9
When brains of the deceased were studied for gender differences, there was a clear difference between men and women in the size of the bed nucleus of the stria terminalis, a key center linked to gender. It was bigger in men, and the difference seems to finalize in early adulthood, long after the window of influence of hormones or medications on the growing fetus or infant. In another study, several brains were studied that were from male-to-female transsexuals, and in every case, the brain center size corresponded with that in females. In a female-to-male transsexual’s brain, this area was the size of a male’s. Interestingly, when the specimens from adults who were exposed to high levels of the opposite sex’s hormones were examined, there was no effect on this brain center’s size. This brain center is hardwired and seems to be a determinant of whether you feel like a man or a woman, and whether you are unfortunate enough to feel that you are in the wrong body.10, 11, 12
This recent understanding about brain sex raises a question about performing surgery to create female genitals for males born with atypical genitals or to create female genitals on females born with male-like genitals. The brain gender doesn’t always match the body, but it’s much harder to reconstruct male parts—outies—than female parts—innies. There is a movement to defer these complicated decisions until the child is old enough to make the decision. This may seem straightforward, but in some cases the reconstruction of the pelvis and urinary tract is a matter of life and death and surgery of the genitals must be decided on immediately. Sometimes the gender of the child will be out of sync with the genitals, making navigating gyms and public bathrooms a challenge. For some, early surgery provides a welcome normalcy to childhood and adolescence.13
Figure 7 Deep brain center determines what gender you feel like
Gender identity disorder (also now known as gender dysphoria) is defined as “the desire for at least 2 years, to live and be accepted as a member of the opposite sex, usually accompanied by the wish to make his or her body as congruent as possible with the preferred sex through surgery and hormone therapy.”14 This condition is finally being recognized as a legitimate and common problem. The underlying cause is not likely a “choice,” but rather a brain gender issue. It is estimated that more than 15 million people worldwide feel like they were born with the wrong goods.15 This is much more of an issue for men than women, at a rate of about 4 to 1, although women haven’t been asked as much, so the true difference could be less.16
So what’s a girl/boy to do? Now that gender dysphoria has been recognized, treatment has become more widely available. These trans men and women are no longer as “trapped” in their bodies as were their predecessors. Modern surgical techniques, coupled with carefully monitored hormone therapy, have enabled transgender people to achieve emotional and psychological relief and satisfaction with their bodies.17, 18 Caitlyn Jenner is currently the most famous transsexual, having transitioned from Gold Medal Olympian and Kardashian stepdad Bruce Jenner. She writes in her memoir, The Secrets of My Life, “The surgery was a success, and I feel not only wonderful but liberated.” This is the sentiment of more than 80 percent of trans men and trans women who undergo gender reassignment surgery.19 Still, it’s a very big step and not taken lightly. Candidates for surgery must demonstrate that they really need it because it’s permanent, costly, and high stakes from the standpoint of risks, complications, and recovery.20
Gender reassignment surgery does not just involve giving the jewels a new setting. Adult men and women have other gender-typical body parts that may be surgically adjusted, including the face, the larynx (Adam’s apple), the chest, the breasts, and the distribution of fat. Women becoming men typically undergo surgical removal of their internal reproductive organs. Many of these gender body differences are influenced by hormones during teenage growth and development. More attention is now being directed towards teens and preteens who identify as the opposite sex to make their transition easier with hormone therapy so these changes are not as profound and may not require surgery. In many cases, blocking the hormone surge of puberty may be an effective and compassionate intervention, as it allows the child with clear-cut gender dysphoria to sidestep the anguish of hormonal puberty in a body that doesn’t match his/her brain while allowing more time to become certain about a decision for surgery.21
As far as the actual genital gender-bending goes, it is easier to make a vagina than a penis. After all, much of the neovagina (neo means “new” in Latin) is hidden. The neopenis is out front for easy scrutiny. Neovaginas are most often made from the very skin that makes the penis, but it is inverted, like pushing in a belly button. The two chambers that fill with blood to create an erection are removed. The head of the penis is reduced in size but most of the nerves are preserved, and it is then positioned at the top of the inverted-penis-now-vagina. The scrotum is surgically divided in half and so is the perineum (the space between the scrotum and the anus) to remove the testicles and to make space for the new vagina. Each half of the scrotum is altered to resemble labia. There is also some shortening and repositioning of the urethra to enable voiding while seated. This neovagina has sensation, and the person can still orgasm. It has a tendency to contract and become narrowed, so regular use of a dilator and lubricant is recommended. If the penis skin is not adequate to be inverted, a segment of large intestine can be removed and used to create the neovagina.
There are several techniques surgeons may use when faced with the daunting task of creating a penis. A penis, after all, isn’t just for show. It’s got waterworks and needs to rise to the occasion. The goal for a neopenis is for its owner to be able to pee standing up, penetrate sexually, and have sensations of sexual pleasure. A common technique is to use a large flap of tissue from the forearm or thigh and make a tube within a tube for the urethra and the penis. An inflatable penile implant is put inside the neopenis, and testicle implants are put inside the labia, which are sewn together in the middle to mimic a scrotum. The flap has a nerve and blood vessels that can be connected to the nerves of the clitoris and the blood vessels of the abdominal or thigh muscles.
In other variations, a flap of skin fat and muscle may be taken from the side of the chest, but without disconnecting the nerve so that the muscle can still be contracted in order to make the neopenis “hard” for sexual penetration. If sex is not a priority, the clitoris can be surgically detached from the underside of the pubic bone, dropped down, and enlarged. The urethra is surgically lengthened with some nearby tissue and the labia are altered to mimic a scrotum with testicle implants. This neopenis is adequate for urinating standing up but not for sex; however, sexual sensation is not affected because no nerves are cut.
These are complex surgeries and are often done in stages. The typical saga will last from 1 to 4 years, usually with complications. Strictures or leaks can occur where the natural urethra is connected to the neourethra (new urethra). Implants can get infected or erode. Sensation may not be satisfactory, and there is also the risk of infection or even injury and loss of some tissue. The worst complication may be a change of heart. This is rare, but even in this scenario, there can be second chances in the hands of a skillful surgeon.22
Figure 8 Male-to-female gender reassignment surgery
Figure 9 Female-to-male gender reassignment surgery
Penis transplantation is now a reality, but it is reserved for victims of trauma, injury, or cancer. The first recipient, a Chinese patient, actually had his removed 2 weeks later due to a severe psychological reaction, but the second, a 21-year-old who lost most of his penis in a catastrophic circumcision complication, went on to father a child. The third recipient was the first in the United States and had lost most of his penis to cancer. He paved the way for a research team at the Johns Hopkins University, which has subsequently performed penile transplantations for wounded veterans. These transplants must be agreed to by the family of the donor. The costs are high and lifelong immune-suppressing medication is required, but for the recipients, it can be a miraculous gift.23