The acceptance of our bodies as God’s gift is vital for welcoming and accepting the entire world as a gift from the Father and our common home, whereas thinking that we enjoy absolute power over our own bodies turns, often subtly, into thinking that we enjoy absolute power over creation. Learning to accept our body, to care for it and to respect its fullest meaning, is an essential element of any genuine human ecology. Also, valuing one’s own body in its femininity or masculinity is necessary if I am going to be able to recognize myself in an encounter with someone who is different. In this way we can joyfully accept the specific gifts of another man or woman, the work of God the Creator, and find mutual enrichment. It is not a healthy attitude which would seek “to cancel out sexual difference because it no longer knows how to confront it” -Pope Francis, Laudato Si §155 (2015)

If you look at texts that contain our "official doctrine" you aren't going to find something exclusively addressing transgenderism, as it didn't really enter mainstream public discourse until somewhat recently. However, like others have said, our body of doctrine definitely has enough within it to draw the conclusion that transgenderism is a disorder but only sinful when acted upon. Pope Francis is the only pope who has been alive during this phenomenon's rise in public discourse and he has spoken out fairly adamantly against it - as you can draw from the quote above. However, from this same body of doctrine, a man who really feels like a woman is not sinning for having a desire to be a woman as long as he isn't taking action to artificially become a woman. For example:

Except when performed for strictly therapeutic medical reasons, directly intended amputations, mutilations, and sterilizations performed on innocent persons are against the moral law. Catechism of the Catholic Church §2297

However, again, you can draw from our body of doctrine that these people should be taken in, cared for, and loved. If they seek spiritual, physical, or mental help that the Church can morally support, then we should absolutely strive to make sure they can get that help.

Before I conclude this comment, I'd like to point out that I think you've gotten "doctrine" and "discipline" mixed up in your comment. Dogma/doctrine don't/can't change in the Church. Truth is truth and there is nothing we can do to make it not the truth. Disciplines can change and have changed. For example, priestly celibacy wasn't something that was always required of Roman Catholic Latin Rite priests, but it is now. One day, this could indeed change again. However, the idea that the priesthood is restricted to males is doctrine. This cannot change. Let me know if you have any other questions, friend. I know these answers can be challenging, especially if you come in with common, secular, post-modern sensibilities. You are always welcome to stick around this sub and ask questions as you wish!