A woman who transitioned to become a man before returning to her biological sex has spoken of the "lie" she was told by a doctor about the gender reassignment process. 

Ellie, a 21-year-old from Belgium, started medically transitioning as a teenager, first taking testosterone before having a double mastectomy at the age of 17. 

She told the BBC that when she was accompanied by her parents on a visit to a clinic, the doctor informed them that the changes would not be permanent. 

"He told my parents that all the effects were reversible - which is the biggest lie," she said.

"I had done my research, and I knew that this doctor could not be trusted. But I was just so happy that he said that, because then my parents were OK with it."

Her father Eric recalled being reassured by the doctor about the use of hormones and encountering little resistance to his daughter's transition from the professionals. 

"We were still in shock from having a girl who wanted to be a boy," he said. "And the doctor said hormones would be better for her."

He added: "I would've liked to have met someone to give me the words and find arguments to make her wait and think about it longer, but there was no-one."

Ellie went through the detransition process with her girlfriend Nele, from Germany, another former trans man who has reverted back to living as a woman. 

While Nele told the BBC that she doesn't regret her sex change, she says it was a form of escapism from the things she was struggling with.

"The thought of going back was scary, because I transitioned to escape my problems. Detransitioning means facing the things I never managed to overcome," she said.

Together, they have created the website Post-Trans.com as a place where ex-trans people can share their stories.