It has emerged that British children as young as 12 have been given access to drugs that block puberty while they contemplate to have a sex change.
One of the main effects of the drugs is to stunt the development of sexual organs so less surgery will be required if someone chooses to permanently change their gender at a later date.
The monthly injection suspends the onset of adulthood so that young people confused about their gender can be sure of any decision before they take on too many masculine or feminine features.
However, bodily and hormonal changes will continue as normal if the medication is stopped.
Supporters say that the "window" prevents a great deal of mental and physical anguish caused by the maturing of sex organs, facial hair growth and changes in the voice.
But critics argue it only prolongs the agony and can prevent people "growing out" of any feelings of confusion.
The treatment can be prescribed for people diagnosed with Gender Identity Disorder (GID) - a rare psychiatric condition that leaves a person feeling they belong to the gender other than the one they are born in.
Until this month, British doctors were prevented from offering youngsters diagnosed with gender issues any medical intervention before the late stages of puberty usually at 16.
But now the National Research Ethics Service has given approval to the UK's only specialist clinic for GID - the Tavistock and Portman NHS Trust in London - to prescribe the drugs to youngsters from 12 years old.
Dr Polly Carmichael, the clinic director, said the reduction in the age limit will be welcomed by families who would have otherwise had to travel abroad to the US for the treatment.
"The majority of our referrals are 15-plus and we get fewer from a younger age group. Certainly, of the children between 12 and 14, there's a number who are keen to take part," the Telegraph quoted her as saying.
"I know what's been very hard for their families is knowing that there's something available but it's not available here.
"This delay gives us a window to explore together that they are definitely making the right decision. But as professionals we need to be looking at the long term and making sure this treatment is safe," she stated.
The hormone blockers, which are already used for early onset puberty, will only be given to around a dozen children and teenagers selected for an NHS research project jointly run by the clinic and University College London Hospital.
To take part, they will have to meet strict eligibility criteria including having full support from their parents, the existence of long-standing gender identity issues, an ability by the child to give formal consent and an absence of other mental health problems.
Those chosen will go through a series of psychological and medical assessments before receiving the blockers.
But Carmichael said that only around 10 to 20 percent of prepubescent children with GID went on to have a sex change. Around 80 percent in late puberty were likely to have the operation.