She wanted to be a man and went for a sex change operation. But the surgery failed and Mr Nathan Verhelst, born Nancy, felt it resulted in "a monster".
The Belgian, who was dejected and disappointed, decided death was the only option. He then "pleaded" for it, The Telegraph reported.
The 44-year-old was given legal euthanasia, most likely by lethal injection, on the grounds of "unbearable psychological suffering" on Monday afternoon.
"I was the girl that nobody wanted," Mr Verhelst told Het Laatste Nieuws newspaper hours before his death.
"While my brothers were celebrated, I got a storage room above the garage as a bedroom. 'If only you had been a boy', my mother complained. I was tolerated, nothing more."
Mr Verhelst had hormone therapy in 2009, followed by a mastectomy and surgery to construct a penis last year. But "none of these operations worked as desired". "I was ready to celebrate my new birth," he said.
"But when I looked in the mirror, I was disgusted with myself. My new breasts did not match my expectations and my new penis had symptoms of rejection. "I do not want to be... a monster."
Professor Wim Distelmans, a cancer specialist who carried out the euthanasia, is the same doctor who last December gave lethal injections to congenitally deaf twins who were frightened they were also going blind.