His boyfriend was also keen for him to go ahead with the sex change because 90% of the people they passed in the street said something nasty. They see it as someone who is consciously acting dirty." Being diagnosed as a transsexual makes it a medical condition, not a moral one.

"When he goes out in female clothes and has a female appearance it is easier for me to persuade myself that he is a girl. For Anoosh's younger brother, Ali Reza, it was harder to come to terms with Anoosh's desire to become a woman. Once a doctor has made a diagnosis - and an operation is in the pipeline - the transsexual can get official permission from his local government official to cross-dress in public.

His father threatened to kill him if he went ahead with surgery.

Despite increasing numbers of Iranian-American physicians practicing in the United States, little is known about the barriers that may impact them as providers of sexual health care.

This is an important topic as discussions of sexual topics are generally considered a taboo among Iranians.

If they want to change their gender, the path is open," says Hojatol Islam Muhammad Mehdi Kariminia, the religious cleric responsible for gender reassignment.

He says an operation is no more a sin than "changing wheat to flour to bread". "The discussion is fundamentally separate from a discussion regarding homosexuals. Homosexuals are doing something unnatural and against religion," says Kariminia.

"Diagnosed transsexuals" Sex changes have been legal in Iran since Ayatollah Khomeini, the spiritual leader of the 1979 Islamic revolution, passed a fatwa - a religious edict - authorising them for "diagnosed transsexuals" 25 years ago.

Today, Iran carries out more sex change operations than any other nation in the world except for Thailand.

My goal was simply to find my own identity." Like many young people in Iran, Anoosh struggled to reconcile his sexual identity with the wishes of family, community and culture. Anoosh's mother, Shahin, raised her children alone and had high hopes for her son. She thinks that part of what is driving many of the boys to operate is the desire to avoid shame.

He says he was continuously harassed and threatened with arrest by Iran's morality police before he had his sex change. "If you are a male with female tendencies, they don't see that as something natural or genetic.

"I always wanted a daughter and I think it's a gift from God that I finally got one." Transsexual in Iran will be broadcast on BBC Two on Monday 25 February 2008 at 2100 GMT.

The original film, Be Like Others directed by Tanaz Eshaghian had its premier this month at the Berlin Film Festival.

After surgery Ali Askar - now renamed Negar and aged 27 - said that after the sex change operation she was initially depressed.