I find myself unconsciously adjusting to "blend" when I'm around men - I'm not very comfortable around guys, so I seem to just shift into deeper voice, squared shoulders, etc. before I even know it. I hate that it sneaks up on me like that, but it's something I'm working at really hard. It's not a psychological shift though - I still identify strongly as female, it's really just a protection mechanism.
On the other hand, when I'm around people I know, or who I know aren't a threat, I tend to just act naturally, as my real, female self. And even though I'm not out at work, I find that people sense the difference, even if only subconsciously - the women at work have started reacting quite differently to me 0 way more open and relaxed, whereas the guys tend to be quite uncomfortable around me. I don't do anything overtly different, but I think it's just a question of the body-language and voice and stuff being very-much at odds with the picture they see.