There's the intriguing suggestion that gender and species are 100% identified with each other on Deltritus: all nymphs are female, all satyrs are male. So, to transition from your birth-assigned sex, you may also have to transition from your birth-assigned species. The idea of changing one's official species does crop up occaionally in SF and fantasy. Offhand I can think of Captain Carrot from Discworld, a human orphan who was adopted by Dwarves and who considers him self to be a (6-foot-plus) Dwarf. In "Translation State" by Anne Leckie there are a couple of examples of characters changing which species they identify as. But I've never seen it linked to gender in this way before.