I would advise instead of making some kind of announcement, just don't conceal you are bipolar if the issue arises. Like someone wants to know why you are acting a certain way, or you had to take a mental health day, the topic of you being on meds causing your weight gain, I don't know, something like that.
I'm not at all afraid to tell people I'm bipolar, but 99.9999999% I do it's because someone's pressuring me to drink alcohol. I tell them I don't drink, they ask why, I tell them I take medication that I'm not supposed to drink while I'm taking it, they ask what it's for, I tell them it's for bipolar disorder. IMO there's nothing really to hide, but it's not something to make an announcement about either.