ok so like I think this is my first time posting in this section but I kinda need your help :-)

I have a friend who is FtM and wanted me to ask a question.
He wanted to know if his "breasts" would shrink once on testosterone, like he's only an A cup so he thought he might be small enough for testosterone to do its thing.

sorry for the random question and thank you

They are likely to shrink some. Can't really say if they will go completely. Most likely not. 

It's possible for some shrinking to occur especially since he is only an A cup but nothing substantial though.

Hello

Yeah I think my mate said he was an A cup or sommat and his have shrunk but not gone completely. He will still need surgery I imagine.

T and building muscle should shrink them a little. In my experience, since I started working out and doing pushups regularly and building up the chest muscles, there has been a lot of shrinking. I went from a B cup to an A.

it can take away the fat of the breast, which will make them shrink but breast tissues can only get away by surgery.

They shrink but not a lot, and how it looks depends on his skin and shape and age. It's not going to be a miracle or anything but it makes binding easier.

For what it's worth I started with a C-B cup. Between T & working out I now am down to an A that is barely noticeable if I'm lying down, even with my shirt off. Standing, there's a definite bulge, but an Underarmor shirt is sufficient to keep them compressed. Granted, when I started T I also started strength training so my body composition was somewhat guided.