Skyler was counting down the days. In just a few months, the 14-year-old would attend a life-changing medical appointment. It would be the first step toward resolving body and identity issues that the teenager had been struggling with for years.

Skyler's sex at birth (or, to use trans terminology, his “assigned” gender) was female, yet he did not readily identify as a girl. From the age of four, Skyler hated wearing dresses, which he would rip apart with scissors. “It didn't feel like me,” he says. Later he did not understand why he was told not to play football, soccer and kickball with the boys.

His confusion grew painful over time. Skyler's first period, at age 11, was traumatic. Every month he would spend an entire week at home, unable to face school. “I was at war with myself,” he says, “and I struggled with depression. I'd pick at my skin and cut myself on my arms and shoulders and legs to distract myself.”

By seventh grade he had learned about transgender identities at his public school. There had been a few other transgender children in the district, and he realized he felt trans. He began binding his size-DD breasts, albeit awkwardly and painfully, and investigating blogs, articles and YouTube videos on being transgender. He learned about puberty blockers, which could stop all further sexual development, but given how womanly his body had already become, thought—mistakenly—it might be too late for that option. “I just started to give up,” he says. “And that's about the time I came out to my mom.”

His mother, Corina, a preschool teacher, had long been concerned about Skyler's gender issues. She was supportive and, with the help of transgender advocate Aidan Key of Gender Odyssey, began seeking experts to help her child. In eighth grade Skyler came out at school, becoming the first openly trans kid there. Although there was some fumbling at first, the teachers began adopting masculine pronouns for him and using his new trans name, Skyler. After a long struggle with the administrators, the school finally created one gender-neutral bathroom for him to use.

Despite these initial hurdles at school, the cutting stopped. He finally felt “more at peace” with himself. But the challenge of a medically assisted biological transition remained. After a long wait, Skyler at last had an appointment set for November. The doctor would examine his physical health and review his gender history, psychological health, emotional maturity and a host of other details. But what would follow was unclear. In a case like this, a physician might prescribe puberty blockers to stall further development or—as Skyler hoped—cross-sex hormones to begin the development of more masculine attributes. Skyler got his wish. After a few months of testosterone, he says, “I feel like I'm really me, more masculine and proud. My mom says I walk taller. At the store, more people call me ‘Sir.’”

It is hard to imagine a more momentous and complex set of decisions than those faced by young trans people like Skyler and the clinicians who seek to help them. As the media has spotlighted trans celebrities such as television personality Caitlyn Jenner and actress Laverne Cox and as society begins to better understand and accept trans people (perhaps even in the U.S. military), demand for medical and psychological support has exploded. But the biggest challenge—medically, psychologically and ethically—is the growing number of children (some as young as seven or eight) seeking treatment despite uncertain medical science. Distressed but supportive parents have been flooding the small number of U.S. clinics that specialize in helping transgender youth. In Los Angeles, for example, the Center for Transyouth Health and Development at Children's Hospital Los Angeles saw close to 400 patients in 2014 versus 40 in 2008. The center is currently adding three to four new patients a week.

No one can say how many transgender people are out there. A 2011 meta-analysis of population surveys from the University of California, Los Angeles's Williams Institute suggests that 0.3 percent of people in the U.S. feel strongly that they are transgender. One of the studies included in the analysis—from the University of Michigan—found that between 0.1 and 0.5 percent of Americans have taken medical steps to transition. Whether trans individuals take those steps or not, they are a vulnerable population. Transgender youth, according to a 2015 Boston-based study of data from electronic health records, face two to three times the risk of their peers for serious psychological issues, such as depression, anxiety disorders, self-harm and suicide. They urgently require attention.

Yet this area of medicine is so new that few clinics have enough qualified and experienced professionals to adequately screen these children and youth. A protocol, developed by Dutch scientists in the early 2000s and adopted by the international Endocrine Society, serves as a guideline for doctors helping young people transition, and researchers have recently confirmed that this approach yields good results for most patients. But clinicians are now debating how closely to follow it. A growing number of trans experts believe the recommendations are too cautious, that screening procedures are too onerous and that young people are forced to wait too long for treatment that could alleviate their misery. Veterans in the field counter that caution is essential given that treatment is largely irreversible and that gender identity can be fluid in the young, with some patients having second thoughts. A paucity of research makes it difficult for both sides to resolve the debate and determine what is best for their patients.

Insistent, Consistent and Persistent

As newly alerted parents arrive at clinics with boys who sew and dress in frilly outfits and girls who would not be caught dead doing either, experts have to diagnose whether these children have gender dysphoria. In this condition, people suffer distress because of a mismatch between the gender identity they experience and their biological sex as determined by chromosomes, gonads and genitals. (Until 2012, psychiatrists classified the condition as “gender identity disorder,” a term now viewed as stigmatizing.)

Although adolescents may confuse the two, gender identity is different from sexual orientation. Norman P. Spack, a pediatrician, pediatric endocrinologist and founder of the gender clinic at Boston Children's Hospital, borrows language from one of his first transgender patients to explain: “Sexual orientation is who you go to bed with. Gender identity is who you go to bed as.” In fact, Spack adds, “I could never predict the sexual orientation of my patients.”

Furthermore, gender dysphoria is more than just rejecting the social and cultural roles assigned to a given gender. Many kids push back against these norms—as when a young boy rejects macho roughhousing to playing house or a girl prefers toy soldiers to dolls—without any discomfort regarding sexual or gender identity.

But for some children, there is a nagging, painful conviction that the gender they are forced to present to the world does not reflect their true self. “There's a small subgroup of trans kids who, as soon as they can talk, are saying, ‘I'm not the gender you think I am,’” says psychologist Diane Ehrensaft of the Child and Adolescent Gender Center at the University of California, San Francisco, Benioff Children's Hospital. Often, Ehrensaft says, these kids do not like their bodies.

Among children under the age of about 12 who cross-identify, in terms of how they dress and behave, only a minority will continue to see themselves as transgender after puberty. A 2008 study by psychologists Madeleine S. C. Wallien and Peggy T. Cohen-Kettenis, both then at VU University Medical Center in Amsterdam, followed 77 children who had been diagnosed with gender dysphoria between the ages of five and 12. At age 16 or later the researchers found that 43 percent of the teens were no longer gender-dysphoric and that 27 percent remained so (some could not be reached for follow-up). Of those who stopped cross-identifying, all the girls and half of the boys were heterosexual; the other half of the boys were either homosexual or bisexual.

In what has become the mantra of the field for recognizing clear-cut trans children, they are “insistent, consistent and persistent over time” in their identification with the gender opposite to the one that they were assigned. A 2013 study led by Thomas D. Steensma, a psychologist at VU University Medical Center, confirmed that the intensity and persistence of identifying with the opposite, nonassigned gender are powerful indicators in predicting who will remain trans. Working with 79 boys and 48 girls referred for gender dysphoria to VU University Medical Center before age 12, Steensma and his colleagues measured these factors through a questionnaire assessing cross-gender behavior through early childhood. At age 15 or later only 23 of the boys and 24 of the girls had persisted. Those who remained trans were more likely to have been insistent early on, saying, for example, “I am a boy” rather than “I wish I were a boy” or they would grow up to be a daddy, not a mommy. Still, Steensma cautions, it is hard to predict whether any specific child will persist as transgender.

Some children change their mind at critical junctures, such as after undergoing a “social transition” (changing their name, pronoun and appearance to live in their affirmed gender) or taking puberty blockers. Some children, Ehrensaft says, gradually realize that they are trans. Still others are more focused on gender expression: wishing to be the other gender and cross-dressing but in a playful, fantasy context, without any distress about their body. Some, she says, are “proto-gay” and likely in adolescence to come out as gay, lesbian or bisexual. Increasingly, many will identify as gender queer, saying, in effect, “I do not identify with either gender; I'm beyond gender” or “I do not fit into your male/female binary.” Such kids, Ehrensaft says, “are our littlest gender outlaws.”

Teens who identify as trans, says psychologist Laura Edwards-Leeper of Pacific University, may also be reacting to peer influences, family dynamics, or religious or cultural beliefs. In some cultures, for example, she says, individuals face less stigma for being transgender than for being homosexual. So it is complicated.

Setting the Standard

In many respects, the Netherlands serves as an exemplar for supporting trans and gender-questioning people. In October, Loiza Lamers (born as Lucas Lamers) won Holland's Next Top Model, the first transgender winner from any country. One Dutch teenager who began her social transition early in life feels that her experiences today are no different than those of her contemporaries. “I'm like any other high school girl,” she says. “I love my dogs, spending lots of time with my girlfriends, going dancing.”

The degree of social acceptance in the Netherlands may reflect the country's long history of working with the trans community. Since 1975 clinicians at VU University Medical Center have counseled 5,000 adults and helped many hundreds of people transition to a different gender. As younger people came forward seeking guidance, Dutch experts established a second clinic for children and adolescents at University Medical Center Utrecht in 1987 that has since joined VU University Medical Center's clinic, known as the Center of Expertise on Gender Dysphoria. To date, they have counseled 1,000 young people, including some who, like the Dutch teen, have pursued a transition.

The procedure these clinicians developed became a template of sorts for the Endocrine Society's standards of care, now used around the world. The protocol first requires a series of psychological assessments. Given the potential fluidity of identity in a young person, careful screening is considered essential to identify which children should undertake the process of transitioning. Assuming kids meet the diagnosis of gender dysphoria, clinicians advise parents to wait until after puberty to see whether their child will persist. (Meanwhile many parents, with or without clinicians' encouragement, may help their children make a social transition before puberty.) At what doctors refer to as Tanner stage 2, when girls have tiny breast buds and boys have slightly enlarged testes, they can receive puberty blockers to prevent further sexual maturation. This stage's onset is variable but usually occurs between 10 and 12 years of age. At around age 16 those who persistently identify as transgender can receive cross-sex hormones, and at 18 they can elect to have gender-reassignment surgery. Throughout the process, the transitioning person must receive mental health support.

According to the first long-term research findings, young people who receive this kind of care do quite well. A 2014 study by psychiatrist Annelou L. C. de Vries of VU University Medical Center and her colleagues reported good results for 55 young people followed from before puberty suppression until after cross-sex hormonal treatment and surgery. Over this period, their psychological functioning steadily improved—with declining levels of gender dysphoria and anxiety and a greater sense of overall happiness. After treatment, their sense of well-being was similar to that of their peers who were not trans. All these transgender youth had identified as trans in childhood, de Vries says.

These recent positive outcomes are based on strict adherence to the protocols. But increasingly in both the U.S. and the Netherlands, with this research as a baseline, clinicians are making treatment decisions on a case-by-case basis. Guidelines recommend waiting until 18 for body-altering surgery, for instance, but some trans boys are having the most common operation—“top surgery,” or breast removal—as early as 13 because binding breasts can cause pain or physical problems.

Even the Endocrine Society is revising its guidelines to be more flexible, says society committee member Stephen Rosenthal, a pediatric endocrinologist at the U.C.S.F. School of Medicine. Although “around 16” will still be the recommended age for cross-sex hormones, for example, newer standards will recognize “compelling reasons” to start earlier, such as to safeguard a child's physical or emotional welfare.

Parents are part of the push to address cases more individually. Gender transitions are complex at any age, but for a minor there is the added complication of reliance on adult guardians for consent and support.

Helping Younger Children Thrive

At age three, reports Marlo Mack (a nom de plume for her podcast How to Be a Girl), her child looked in her eyes and said, “Mama, something went wrong when I was in your tummy that made me come out as a boy instead of a girl. Put me back so I can come out again as a girl.” For nearly a year Mack resisted her child's entreaties to be a girl. Then she grieved for her lost boy and loved and accepted her new daughter, a “girl with a penis.”

Their therapist, Mack says, urged her to “take a wait-and-see attitude,” at least until age five, before supporting a social transition. “I tried to do it,” Mack says, “but I felt unsupportive and almost abusive.” Thus, at the age of four and a half, Mack's child became a girl at home and in the world.

There is no medical treatment for prepubescent transgender children, but a growing community of clinicians is cautiously endorsing social transitions. Mack is one of an increasing number of parents in the U.S. who are helping their preschoolers to live as the gender they feel they are. In the Netherlands before the year 2000, Steensma says, almost none of the children referred to the Amsterdam clinic for gender dysphoria were presenting socially as their affirmed gender. By 2009 that percentage had risen to more than 33 percent, a reflection of similar parental support.

The most important question surrounding a social transition, according to psychiatrist Scott Leibowitz of Ann & Robert H. Lurie Children's Hospital of Chicago, is whether it helps the child thrive. Suppose a boy will not go to school except in a dress? “If a kid does go to school in a dress and does well,” Leibowitz says, “I support it.”

There is one big caveat for parents: be open to your child changing back. Families who, for example, have grieved their lost daughter and finally, painfully, accepted their new son may find it difficult to tolerate the ambiguity of their loss/gain. With the greatest love and best of intentions, they can trap their child in a mold that no longer fits. Edwards-Leeper recalls one patient who told her, “I can't change my mind. My parents have done so much for me.”

In a 2011 review of adolescents at the Amsterdam clinic, Steensma found that children who had transitioned socially were indeed more likely to remain trans than those who had not come out in their community. But he is unsure whether the social transition helped or hindered all of these kids. For instance, Steensma says, two adolescent girls who were no longer trans struggled for some time to change back to their female identity because of “fear of teasing and shame to admit they had been wrong.” He wonders whether counseling children on coping with their gender variance until early puberty might be a lesser evil than having them make a complete social transition twice, including a name and pronoun change.

“One True Test of Gender”

Adolescence is a powerful time—physically, psychologically and socially—in determining lasting gender identity, experts say. At this point, young people often decide who they are and are not. Some young people may discover they are or may be trans. In a 2011 qualitative study of 25 teens, Steensma found that along with feelings about the changes in their bodies, the children's responses to a new social environment provided clues to their gender identity. They were now confronting a world in which boys and girls divide and hang out with their same-sex peers. They might have also been experiencing their first sexual and romantic feelings.

Despite pressure from an increasing number of parents to use blockers before Tanner stage 2 and the onset of puberty, the medical community agrees that waiting is essential. “Some parents are so convinced their child is trans,” Spack says, “that they don't want their child to have any natural hormones. These parents bring their kids in as young as age seven or eight. If we did that, we'd take away the one true test of gender: puberty. If the kid accepts the body they get at puberty, how can the parents say, ‘My child is in the wrong body?’”

At or after Tanner stage 2, endocrinologists administer puberty suppression through either leuprolide acetate injections on a regular basis or surgical insertion of an implant that slowly releases histrelin. These are drugs that mimic the body's natural signal to stop producing hormones.

Doctors who treat trans kids say that puberty blockers are probably safe. Initially there had been concern about a negative impact on bone density, which normally increases during puberty. Fortunately, studies that followed children who had taken these drugs for “precocious puberty” into adulthood found that they appeared to have relatively normal bone density and no other serious effects—at least for the 30-year follow-up period, says pediatric endocrinologist Daniel Metzger of BC Children's Hospital in Vancouver.

After kids stop taking blockers, the effects disappear within six months, and they resume their natal puberty or take cross-sex hormones and go through puberty as their affirmed gender. Some kids remain on blockers when they take cross-hormones to prevent any unwanted pubertal changes that could happen on small doses of cross-hormones.

The medical purpose is to temporarily halt menstruation and the development of breasts, beards and other sexual characteristics, reducing the need for later surgeries and procedures and enhancing the quality of any gender change. Doctors often determine the length of treatment to prolong growth for trans boys and to curtail height for trans girls.

Psychologically, blockers reduce the distress of adolescents who, like Skyler, might otherwise harm themselves in reaction to pubertal changes. Most of all, puberty suppression gives young adolescents additional time to mature, to determine their true gender identity and to more fully evaluate the irreversible effects of taking the next step: cross-sex hormones.

Despite compelling need, some adolescents cannot get blockers. They may be too far into puberty when they recognize themselves as trans or may not be able to afford the treatment, which is often not covered by insurance. Injections of leuprolide acetate cost $700 to $1,500 a month, and histrelin implant surgery totals about $15,000. Cheaper substitutes such as progesterone have potentially serious side effects, including the risk of blood clots. For these reasons, some doctors may start young teens on more affordable cross-sex hormones instead of blockers.

A Rift in the Field

At each stage of transitioning, parents and clinicians have begun questioning the existing standards, particularly for children who appear to be “clearly” trans and therefore might benefit from a different approach. Some of these transgender youth specialists, such as pediatrician Johanna Olson, director of the Center for Transyouth Health and Development, consider themselves as advocates for the children. “We have no specific, lengthy, neuropsychiatric screening protocol,” Olson says of her clinic. She feels that current measures of gender dysphoria are inadequate. “Our model is to listen to the young people. They are like snowflakes. They each need an approach that is individually tailored to their needs.”

Perhaps the most controversial issue in the transitioning process is how long teens should wait before taking cross-sex hormones—for trans females, this means estrogen and antiandrogens; for trans males, testosterone. Among their other results, estrogens produce feminizing effects such as enlarging breasts and distributing fat in a more female pattern. Testosterone halts menstruation and promotes the growth of masculine-type body hair, male muscle mass, voice deepening and other male characteristics.

Depending on when puberty begins, it could easily take half a decade before someone qualifies for this step, according to the strict protocol. More and more, the “advocate” side of the field has called to stop keeping these children “on the sidelines” while their peers go through puberty. For clear-cut trans kids, therefore, many clinicians are increasingly comfortable giving cross-sex hormones at 14 or even younger.

But veteran practitioners, such as Edwards-Leeper, worry about moving too fast. As at other stages, the concern remains that a young person may not persist in a trans identity yet feel pressured to continue. Some patients, she says, feel as though they are “‘stuck’ in a gender or on a runaway train that is hard to get off.” And unlike earlier stages, the stakes are higher: cross-sex hormones have irreversible effects on physical development.

Added complications arise with adolescents who only at puberty discover they may be trans. Payton McPhee of British Columbia is an example. A tomboy as a child, Payton began questioning his gender at 11 as friends began getting crushes. At 13 he realized he was attracted to girls. He came out as a lesbian, he says, “but it still didn't feel right.” At 14 he met his first trans person and looked up “female-to-male” online. He was transfixed. “I was excited to finally have something to call myself,” he says.

With the support of his parents and doctors, Payton began taking birth-control pills to reduce his period to twice a year. By binding his breasts and doing vocal exercises to lower his voice, he says, he can “pass” as a boy. Now 15, he would like testosterone therapy. But his parents and doctors are not yet convinced. “His psychiatrist said that at the very least, Payton is gender-fluid,” reports his mother, Sarah McPhee, “and most likely transgender.”

Clinicians are seeing kids like Payton show up in increasing numbers. But whether they should get cross-sex hormones, wait or take small doses for a short time to “explore” their gender is an open question. Some kids may be confused, says Harvard Medical School psychologist and gender expert Amy Tishelman, “and this is a way to glom onto an identity.” These kids may turn out to be trans. Or they may be more gender-fluid and need to experiment.

Dianne Berg, a psychologist and gender expert at the University of Minnesota, has seen some transitioning adolescents who identify as neither stereotypically male nor female and have parents pushing them to fit a more traditional mold. “It is hard for parents to wrap their head around their teen saying, ‘I want to be a man, but I don't want to be a manly man—I want to be a more feminine kind of man,’” Berg says.

Metzger recalls a female-to-male patient who, at 13, wanted to transition and, at 16, got testosterone. Halfway through treatment, when the patient had a little facial hair and a bit more male bone structure, he asked to go on a lower dose, telling his doctor he was “a femme kind of boy.” Metzger believes he has since had his ovaries removed and has remained on a lower dose of testosterone. “Is that safe?” the endocrinologist asks. “No one knows the answers.”

Difficult Trade-offs

One of the thorniest issues about age is whether an 11- or even 14-year-old can understand the implications of a treatment that means he or she can never have biological children. Although it is theoretically possible for adolescents to experience enough natal puberty for boys to preserve sperm and girls to harvest eggs, it is rare for natal males to do this, and clinicians say that natal girls categorically reject it. Thus, in effect, when adolescents agree to cross-sex hormones, they or their parents are consenting to lifelong infertility.

Can a young teen understand this? It depends. As 22-year-old trans male Zachary Kerr of Methuen, Mass., recalls about the decision to take testosterone, “I blocked out everything that wasn't good because I wanted it. I was 16. I didn't care.”

Other clinicians say that parents must choose for their children, just as they would if a treatment for cancer resulted in permanent infertility. “For some of these kids,” says Michele Angello, a psychotherapist and gender specialist in Wayne, Pa., “the outcome is grim if we don't treat.” As it is with so many issues these young people face, families and clinicians must recognize that each case is unique and that there are risks on every side. “There is no one right answer,” Olson says. “Trans kids throughout life have to decide between bad choices.”

More broadly, it is this keen awareness of the challenges that young trans individuals face and the limits of current knowledge that motivate concern on both sides of ongoing debates. Day to day, clinicians are doing their best to navigate between the known and unknown, but answers to at least some key questions may soon be coming. In August 2015 the National Institutes of Health awarded $5.7 million to four major transgender centers for a five-year study of the physical and psychosocial outcomes of treatment for transgender youth.

Ultimately the best course will be to balance the ability to individualize care with caution. “Those of us doing this the longest,” Edwards-Leeper says, “feel more concern. Because we see how complex these cases are, and we understand brain development and child and adolescent development. Some newer doctors who just want to advocate for the children can lose sight of the bigger picture.”

And both clinicians and families agree that a larger battle of acceptance and tolerance is still being fought. Despite the outpouring of government research funds, media attention and transgender pride in places such as Los Angeles and Seattle, it is important to remember that through great swaths of this country, trans kids face ignorance, blocked pathways and stigma.

Lenessa (not her real name), a gentle, soft-spoken 15-year-old trans girl from a small town in Texas, came close to becoming a statistic at age 11. From her youngest childhood, she had wanted to be a girl and wear “flowy” dresses, she says, but she was not allowed. While her two brothers roughhoused outside, she would read and sew indoors. The start of puberty was a shock. “I will never forget how horrible it was,” she says. “It started to become permanent that I was a boy—becoming a man.”

When, with her mother's help, she realized that she was trans and told her family, her father and grandmother rejected her. “Except my mom,” she says, “everyone I loved seemed not to want to be with me. That's when I really didn't want to live.” To protect her from her suicidal impulses, her mother took her to a psychiatric hospital. For her father, it was “a wake-up call.” “I wanted a live child,” he says, “not a dead son.”

Even with both parents agreeing, finding a way forward was hard. Neither Lenessa's school nor her pediatrician had ever heard of being trans. Long searching led them to Ximena Lopez at the gender clinic at Children's Medical Center Dallas, which is affiliated with the University of Texas Southwestern Medical Center.

Today Lenessa is on blockers and, her father says, is flourishing. They have moved to a place where no one knew them before, and the girl who is now Lenessa will start high school in the fall, wearing the dresses that she loves. She hopes to eventually start hormones and develop a more womanly body. She says she understands the sacrifice she will be making: “It makes me sad when I realize I can't have my own children. But sometimes in life, when you really want something, you have to accept things you don't like.”


Where Does Gender Live in the Brain

Some children insist, from the moment they can speak, that they are not the gender indicated by their biological sex. So where does this knowledge reside? And is it possible to discern a genetic or anatomical basis for transgender identity? Exploration of these questions is relatively new, but there is a bit of evidence for a genetic basis. Identical twins are somewhat more likely than fraternal twins to both be trans.

Male and female brains are, on average, slightly different in structure, although there is tremendous individual variability. Several studies have looked for signs that transgender people have brains more similar to their experienced gender. Spanish investigators—led by psychobiologist Antonio Guillamon of the National Distance Education University in Madrid and neuropsychologist Carme Junqué Plaja of the University of Barcelona—used MRI to examine the brains of 24 female-to-males and 18 male-to-females—both before and after treatment with cross-sex hormones. Their results, published in 2013, showed that even before treatment the brain structures of the trans people were more similar in some respects to the brains of their experienced gender than those of their natal gender. For example, the female-tomale subjects had relatively thin subcortical areas (these areas tend to be thinner in men than in women). Male-to-female subjects tended to have thinner cortical regions in the right hemisphere, which is characteristic of a female brain. (Such differences became more pronounced after treatment.)

“Trans people have brains that are different from males and females, a unique kind of brain,” Guillamon says. “It is simplistic to say that a female-to-male transgender person is a male trapped in a female body. It’s not because they have a male brain but a transsexual brain.” Of course, behavior and experience shape brain anatomy, so it is impossible to say if these subtle differences are inborn

Other investigators have looked at sex differences through brain functioning. In a study published in 2014, psychologist Sarah M. Burke of VU University Medical Center in Amsterdam and biologist Julie Bakker of the Netherlands Institute for Neuroscience used functional MRI to examine how 39 prepubertal and 41 adolescent boys and girls with gender dysphoria responded to androstadienone, an odorous steroid with pheromonelike properties that is known to cause a different response in the hypothalamus of men versus women. They found that the adolescent boys and girls with gender dysphoria responded much like peers of their experienced gender. The results were less clear with the prepubertal children.

This kind of study is important, says Baudewijntje Kreu kels, an expert on gender dysphoria at VU University Medical Center, “because sex differences in responding to odors cannot be in uenced by training or environment.” The same can be said of another 2014 experiment by Burke and her colleagues. They measured the responses of boys and girls with gender dysphoria to echolike sounds produced by the inner ear in response to a clicking noise. Boys with gender dysphoria responded more like typical females, who have a stronger response to these sounds. But girls with gender dysphoria also responded like typical females.

Overall the weight of these studies and others points strongly toward a biological basis for gender dysphoria. But given the variety of transgender people and the variation in the brains of men and women generally, it will be a long time, if ever, before a doctor can do a brain scan on a child and say, “Yes, this child is trans.” —F.R.