It was uncomfortable at first admitting it to my boss and HR. I'm not sure why - I almost felt guilty about doing it, like I was doing something wrong. But they both were pretty understanding. I told my coworkers as well, and they have all been fairly supportive. They ask how my progress is going, and whatnot, which is not nice. I personally would recommend just coming out and saying it. You don't have to go into detail, or elaborate on it. Give a simple answer, and leave it at that. They don't need to know all the details if you don't want them to.