Grace, you're pretty advanced in your transgender journey, so maybe in this job you don't really need the support of your work colleagues in the way you did in your former job?
It's obviously a totally personal preference to be able to share whatever you choose with your work colleagues. Truly, if I were to change jobs at some point, I wouldn't even discuss my gender history - I'm just a girl.
You'll find the right moment, like, as you said, if the topic of transgender health comes up at a meeting. Until that time, you have the advantage of no history or predetermined perceptions, so I wouldn't give your colleagues any ammo until you're well and truly entrenched.
But if you find youself in the position of having to defend transgender people, then, if I was in your shoes, I wouldn't hesitate to out myself and help educate my colleagues, gently, but firmly.
Hugs
Julia