Girl/Boy Interrupted

That positive outcome seemed to agree with follow-up studies of Dutch adolescents that indicated those who started hormone therapy between 16 and 18 were more satisfied with their sexual reassignment surgery and had fewer psychological problems than people who started transitioning in adulthood. Meanwhile, Dutch psychologist Dr. Peggy Cohen-Kettenis was seeing younger and younger patients with GID, many of whom were so distraught that they couldn't start hormones until 16 that therapy couldn't reach them.

So about seven years ago, the Amsterdam Gender Clinic became the first in the world to regularly block the early and still reversible stages of puberty, provided that the patients met strict requirements: Their GID had persisted since an early age, they were otherwise psychologically stable, and had a supportive family.

The clinic has treated around 60 adolescents between the ages of 12 and 16 so far with the GnRH blocker, about half of whom were referred early enough to start shortly after the onset of puberty. For those who had reached the middle stages of puberty, the drug could slightly reverse and stop any further development. All patients decided to start hormones of the target sex once they became eligible at age 16.

Ever since the first forays into treating humans with cross-sex hormones in the 1930s and '40s, men taking estrogens and women testosterone has brought on expected changes. But by blocking puberty first, the changes can start on a blank canvas, resulting in a closer replication of the opposite sex's development. With estrogens, biological boys grow breasts, and fat will collect on the hips and thighs to create an hourglass shape. By blocking the growth-spurt-inducing testosterone of male puberty, they'll likely end up shorter — a plus if wanting to pass as a woman. The penis and testes will remain at a pre-puberty size, the voice will not drop, and no Adam's apple will jut out. The face will not grow rugged ridges like that of a man's, although the clinic will take pictures every three months to determine the exact effects on bone structure.

With testosterone, biological girls gain muscle in the shoulders and grow male-pattern body hair. Their voice will drop, an Adam's apple pops out, and the clitoris lengthens a few centimeters. Since they've held off female puberty's estrogen, which tapers off bone growth, they gain time to put on some inches. Height can be further enhanced by growth-stimulating hormones along with the GnRH blocker, and is given one final push by the testosterone-fueled growth spurt. The Dutch doctors say the interventions have been able to add or subtract up to five to seven inches from patients' predicted heights.

With continued counseling, and after having lived for a period as the target gender, both sexes are eligible for surgery at age 18 to remove the testes or ovaries. After that, they stop the GnRH blocker.

Not all countries have such easy access. Hormonal intervention must be approved in court in some countries, and with Lupron costing roughly $500 to $700 a month in the United States, the treatment is out of reach for many families. Some doctors report getting payment from insurance by playing with the wording in the diagnosis — leaving the word "transgender" out — but many others have run into a brick wall with third-party payers, raising concerns in the transgender community that the treatment could create a class division between those who can and can't access treatment.

Without the luxury of delaying puberty with Lupron, some doctors go straight to prescribing cross-sex hormones to kids as young as 12 or 13 to override their natural puberty and allow them to develop as the target sex at the same time as their peers. Cross-sex hormones can cost as little as $25 to $70 a month, a fraction of the cost of Lupron, but many of the changes are permanent.

"Most [adolescents] don't want to just suppress. They want to move," says Marvin Belzer, an adolescent medicine specialist who has started young teens on cross-sex hormones at Childrens Hospital Los Angeles. "In our society in America, starting early has far less bad consequences than starting late."

But not all are convinced starting early is best. The team at the Gender Identity Development Service at the Tavistock Clinic in London will not intervene until puberty is nearly complete, saying the experience may help patients make a more informed decision about being misplaced in their body. Domenico Di Ceglie, the team's child and adolescent psychiatrist, wrote in an e-mail that 20 percent of the adolescents treated in the clinic no longer wanted any intervention once they'd completed puberty.

He warns that the long-term effects of delaying puberty are unknown. He questions whether the puberty-blocking treatment itself could affect a patient's gender identity, since adolescence is a key time for brain development and a possible time for a change in perceived gender.

Then there's the question of bone density: The London team questions whether delaying puberty could cause a long-term deficiency, since bone accrues at a rapid rate with the hormonal flurry of adolescence. The Dutch say their patients' bone density catches up to normal once they begin cross-hormones, but patients will be monitored until age 25 to see if there are any final differences.