Meet the youngest girl in the world to have sex change operation at 16!

Aged just four, and then named Jack, Jackie told her mother Susan "God has made a mistake, I should be a girl."

Trapped in a body she hated, Jackie first overdosed aged 11 and made six more suicide attempts before she was 15. Medicines were locked in a safe and knives had to be hidden away. She threatened to mutilate her genitals.

So, Jackie Green became the youngest person in the world to undergo transgender surgery at the age of 16.

"Without that surgery, I wouldn't be here now," the Daily mail quoted her as saying.

"I'm a girl, I always have been - there's never been any doubt in my mind about that. It's just that my body didn't match because, as far as I'm concerned, I had a birth defect," she said.

Jackie, who is the subject of a BBC documentary to be screened later this month, was diagnosed with gender identity disorder (GID) aged five after being referred by her GP to the Tavistock and Portman NHS Foundation Trust.

The same child psychiatric unit came under scrutiny earlier this year when it was revealed that another five-year-old, Zach Avery, was diagnosed with GID by its experts.

The case elicited concern that medics were pathologising normal childhood curiosity - after all, children often experiment with dressing up as the opposite sex. But the difference was that Zach, like Jackie, had threatened to mutilate himself after tearfully insisting for months he was the wrong sex.

As unusual as they are, experts say both cases highlight the growing medical, and perhaps wider social understanding of GID and transgender.

At present it is not known why some people who are chromosomally one sex feel they are the other, but what is certain is that transgender people often have tremendously difficult lives.

Thanks to her astonishingly supportive parents, Jackie was started on hormone drug treatment at 14, which meant she never underwent male puberty, her voice never deepened, and she never grew masculine proportions or features.

Based on her early rate of growth, doctors estimated she may have reached 6ft 4in, and today she stands a statuesque 6ft.

"A lot of transsexuals have distinctive features, because they haven't been able to take the blockers early like I did. This makes them stand out, making it much harder to fit into society, especially when it comes to a job," Jackie said.

Although medicines are only effective if taken from the first signs of puberty, until recently they were not authorised for use in those under 16.

It seems terribly young but Susan was in no doubt by the time her daughter started hormone therapy.

"As a toddler, Jackie always headed for the dolls in toy shops. Initially, I did think it was a phase but Jack, as she was then, became disruptive in class, ran away from school, loathed having her hair cut and would rip off her school uniform and put on girls' clothes when she got home," Susan said.

Aged eight, Jackie sent an email to everyone at her primary school saying she was a girl trapped inside a boy's body. After that, she started going to school dressed as a girl.

"Jackie was so much better after that, more content than I'd seen her in years," Susan said.

"Of course I knew not everyone would respond well and one mother used to sit outside the school in her car shouting "Freak" and "Tranny" at her. I had to call the police to get her to stop.

"Despite that, her last year of primary school was brilliant. Unfortunately, when she went to secondary school everything fell to pieces and I spent the next two-and-a-half years on suicide watch," she said.

Jackie was bullied mercilessly and took an overdose. Fearing her attempts might succeed, Susan found her a place at a Specialist Inclusive Learning Centre for children with health problems.

"No one knew me so I could go along as a girl and life was a bit happier again for a while," Jackie said.

"Around the age of ten, I remember telling my mum that if I started turning into a man, I would kill myself.

"I was aware that puberty was approaching and that, coupled with the bullying, was too much. I took an overdose of paracetamol and ended up in hospital. Looking back, it was more a cry for help," she said.

With NHS doctors unable to prescribe puberty-delaying drugs or ‘blockers' as they are known, Susan found Dr Norman Spack, a US-based specialist in gender dysphoria, via the internet.

The first stage of treatment involved an injection of a drug that blocks the production of the male sex-hormone testosterone. Next, tablets containing a synthetic version of the female sex-hormone oestrogen was given - a process known as cross-hormone therapy.

"The first time I noticed my body changing was about six months after I started taking the blockers. My breasts started to develop, my face began to get thinner and I began to get a more feminine shape," Jackie added.