Zerophilia (2006)

The film is about a fictional condition affecting less than 1000 people in the world, who have an extra "Z" chromosome. Following their first experience of sexual intercourse, zerophiliacs begin to change gender whenever they are sexually aroused. Luke (Taylor Handley), a young man who is somewhat insecure about his masculinity, begins to exhibit zerophilia following a sexual encounter with a strange woman (Kelly LeBrock). He meets a young woman Michelle (Rebecca Mozo) and experiences partial transformations when they go out together. He confides about his partial transformations to his best friend Keenan (Dustin Seavey), who contacts Sydney (Gina Bellman), a zerophilia specialist from out of town. Sydney persuades Luke to go through with the transformation, which he accomplishes through masturbation. However, "Luca" is unable to achieve an orgasm to change back, even with coaching from Keenan's girlfriend Janine (Alison Folland). After a visit by Michelle's brother Max (Kyle Schmid), who flirts with "Luke's cousin", and whom she watches from the bedroom as he leaves, she succeeds.