[scryer]

It really comes down on the method of change

If the change is biological and the person is undergoing a full change from human to wolf or even to part wolf you have to explain how the change would affect the primary and secondary sex traits. Body fat distribution(body shape/breasts) and hair growth is affected by hormones rather than strictly DNA. So a male body can appear female or a female appear male based upon the hormones produced in the body. This change is more cosmetic as the original primary sex traits remain and require physical surgery.

You could explain the change causes hormonal changes extreme enough to change the appearance from one gender to another cosmetically. Its actually quite easy with the right hormonal changes to give a male breasts and female shape, or to make a female be hairy and male bodyshape.
Changing the primary sex would be a lot more work, like a male body changing the testicles and penis into a vagina and ovaries/uterus, or the reverse in a female body is a far more extreme part of the change, but in the sense of werewolves no more extreme that giving someone a tail or wolf ears, the change is mutating and repurposing the raw organic material of the body.

The main issue with this idea is the change to werewolf would be easier to explain, such as the virus/disease/condition that causes it holds its own sex based DNA to overwrite and change the host, but when they change back the overwritten cells would no longer have the old dna to back to how it was before, so somehow the change into a werewolf would store the human dna somehow, so when the person is a wolf then they carry the "return to human" virus dormant in the werewolf system, like reverse lycanthropy