Last year Sharon Lane* found her 12-year-old son Nick* trying to cut off his penis. Since he was a toddler, Nick has been adamant that he is really a girl. Aged 5, he declared: “God has made a mistake. I should have been born a girl.” A year later he asked, “When can I have the operation to chop off my willy and give me a fanny?”

Nicky - who suffers from a rare condition called Gender Variance (GV), sometimes referred to clinically as Gender Identity Disorder (GID) - started attending school dressed as a girl at the age of 9, unable to “pretend” any longer. She was the subject of constant bullying and harassment so severe that she now attends a special school for “at risk” children.

When Nicky hit adolescence, things just got worse. “She felt like an alien in her own body,” explains Sharon, who describes Nicky as her “daughter”. “When she started experiencing erections, she would scratch her skin raw.”

Nicky has twice attempted to cut off her penis and taken several overdoses. “Sometimes I felt like I was on suicide watch,” Sharon says.

“For children with atypical gender development, puberty can be a very intense and distressing experience,” explains Domenico Di Ceglie, a child psychiatrist at the national Gender Identity Development Unit (GIDU) for children and adolescents in London. “They may experience considerable isolation and can also become the victims of persecution, which may contribute to feelings of depression and misery.”

But just how common is GV in young people? Ten years ago GIDU was seeing 15 cases a year - now it is over 60. Gender discomfort may be detected in children aged as young as 3 or 4, but its outcome cannot be confidently predicted until puberty. In fact, GIDU found that 80 per cent of children experiencing severe GV did not go on to become transsexual adults.

For the remaining 20 per cent, however, puberty can be impossibly painful. Yet UK doctors take a cautious approach and do not consider any form of physical intervention until the age of 16, by which time the body will have undergone irreversible changes.

“By the time Nicky reached 16, it was estimated that she would be 6ft 4in tall, with a square jaw, an Adam's apple and hands and feet of male proportions,” explains Sharon, who is a member of Mermaids, an online family support group for children and teenagers with gender identity issues. “Even if she opted for sex-change surgery later in life, she was always going to look like a man in a dress. The social ostracism she'd have faced would have been awful.”

Convinced that Nicky would kill herself rather than go through male puberty, Sharon has opted to take her to the United States for a controversial new treatment which involves putting puberty on hold, using hypothalamic gonadotropin-releasing hormone (GnRH) blockers. These stop the production of the natural sex hormones (oestrogens and testosterone) that are released during puberty, thus producing a state of “biological neutrality”.

GnRH blockers have been successfully used for many years to treat children who experience premature puberty (before the age of 8) and the effects are fully reversible - when the drugs are stopped, puberty resumes with no apparent side-effects.

About six years ago a team of Dutch doctors at the Free University Medical Centre in Amsterdam, led by the Dutch psychologist Peggy Cohen-Kettenis, began to use GnRH blockers to treat under-16s who were suffering from gender dysphoria. The idea is that delaying puberty relieves the adolescent's immediate distress, giving more time for diagnosis before the development of unwanted secondary sex characteristics that are difficult or impossible to alter.

Once patients reach 16, they can make the decision to receive the sex hormones of their target gender, allowing them to go through an artificial “trans” puberty. Later in life they may opt for gender confirmation “sex change” surgery to complete the process.

Cohen-Kettenis claims that “treatment outcome in transsexuals is significantly more favourable when puberty is suppressed than when treatment is started later,” and over the past few years 14 eminent clinics around the world have started to follow this approach. In Germany, 12-year-old Kim (formerly known as Tim) made headlines as “the youngest-ever transsexual” and newspapers in the US have reported on clinics that they claim are offering “sex changes for 12-year-olds”.

However, not everyone agrees with this controversial new treatment. “Some people hate me for what I'm doing,” Cohen-Kettenis acknowledges. Even among specialists there is fierce debate about the approach. The British Society of Paediatric Endocrinology and Diabetes (BSPED) guidelines currently sanction the use of GnRH blockers only for teenagers who have “completed” puberty, and in any event not before the age of 16.

Russell Viner, a hormone specialist and one member of the team responsible for drawing up the current guidelines, has several reservations about the early use of GnRH blockers. “I am concerned about the effects of suppressing puberty very early, particularly on the brain, which is developing extremely quickly at this age,” he has told The New Scientist.

Puberty, as well as affecting the sex organs, boosting growth and bone density and affecting muscle mass and fat distribution, is believed to have a profound effect on brain development. While the short-term data produced by the Dutch shows no serious side-effects related to growth and bone metabolism, Viner believes that it is essential to measure the long-term outcome of this treatment on the various systems and also to compare outcomes for patients treated using the Dutch and UK protocols. These results, however, will not be available for a number of years.

Viner is also concerned about giving blockers to children who may later have a change of heart: “Despite doing very comprehensive psychological assessments, we find that around 20% of young people who are convinced that they are transsexual change their minds at puberty.” Is it possible that the treatment might alter the natural outcome?

The Dutch team has given GnRH blockers to more than 60 under-16s, and claims not to have had a single patient who has regretted the decision. They believe it is important for children to be exposed to natural puberty, so blockers are not given until puberty reaches what is known as Tanner stage 2 or 3, before irreversible changes occur. They also have a rigid screening programme that they believe correctly identifies those children for whom this treatment is appropriate.

Dr Simona Giordano, the medical ethicist at the University of Manchester Medical School has declared the current BSPED guidelines to be “clinically, ethically and legally questionable,” and they have been met with impassioned protest from GID support groups. Giordano argues that “it is mistaken to assume that clinicians are in no way responsible for the foreseeable consequences of their inaction, which include self-harm and suicidality in gender-dysphoric adolescents who are denied medication to suspend puberty”.

Giordano's concerns are starkly illustrated in a letter written by a 16-year-old to a female paediatric endocrinologist who co-authored the current guidelines: “The last two and a half years have been horrendous for me, with my body becoming so disgustingly adult male that I cannot bear it.

“Imagine how you would feel if, tomorrow morning, you were to wake up to find yourself in a male body, with a man's voice and a man's face looking back at you from the mirror, with early-morning beard and moustache stubble, with no breasts, an Adam's apple, large male feet and hands, a body covered in thick, black hair and a penis and testicles.Would your brain be screaming out, in protest, that you are female, not male? Living in a male body hurts beyond belief. I sometimes feel as if I will go crazy with the desperateness of it.”

This sense of despair frequently leads to extreme pressure being placed on clinicians to act and to provide immediate solutions, explains Polly Carmichael of GIDU, who regrets that the debate has become so polarised. “The by-product of that polarisation is increasing desperation among youngsters, led to believe that there is a treatment which can ‘make it all all right', but to which they are denied access.

“We are not saying that the Dutch approach is wrong, and we are closely involved in research with the Dutch, but we want to do the best we can by the young people we work with, who are a very vulnerable group.”

For this reason, Carmichael regrets the decision of parents such as Sharon to take their children overseas for treatment. “They are then out of the loop in terms of receiving the holistic support they need. It's not just about ‘solving' the problem with physical intervention: a large element of management is promoting the young person's tolerance of uncertainty and resisting pressures for quick solutions.”

The data that the Dutch team has published thus far looks promising, Carmichael says. “But it would be unhelpful and inappropriate to change UK policy without considering the full implications of all the new research and having a proper debate.”

That debate is scheduled to take place in October, when the Royal Society of Medicine convenes a multidisciplinary panel of experts from around the world to discuss the issue. Meanwhile, BSPED has removed the current guidelines from its website, stating that they are under review. Pressure groups are hoping that after the autumn conference these will be revised to come into line with those of the Netherlands.

But Sharon Lane believes the conference agenda is strongly biased in favour of maintaining the status quo, and has no regrets about her decision to seek treatment for Nicky in the US. “We were told that waiting till Nicky was 16 could do no harm, but I knew that Nicky would kill herself rather than go through a puberty she finds repugnant. I couldn't let that happen. I listened to their arguments, but I had a depressed and desperately frightened child and in the end I couldn't let her suffer any longer.”

*Names have been changed