Dan,
One of the things you will want to remember is that everyone's body is different, our circumstances are different, and our perspectives are different. While some are simply unable to handle the thought of a man wearing a bra...no matter how big his breasts...others see it as just an article of clothing designed for a specific and practical purpose. For myself, I drive a bus everyday. It doesn't have an "air-ride" seat, and is in fact only marginally better than the ones the riders get. At times I have generally little breast sensitivity, and at other times I can hardly stand it. This means that since the bus rides like a buckboard, within the first 15-minutes I'm feeling like a milkshake, with nearly 8-hours to go! All that bouncing and shaking drives me absolutely nuts (a shorter trip than I would like to admit)! Nevertheless, it is for these reasons that I wear a bra to work - support and comfort. You may, or may not find yourself in circumstances where the support provided by a bra is worthwhile to you. I would encourage you to weigh the issue on the fulcrum of practicality, rather than on emotion or ego.
That said, a bra really isn't the issue here, at least not at this point. The fact that you are growing breasts is. Before you can really begin to make long-term decisions about how you will handle having them, you will first have to reconcile yourself with the fact that you do have them. At 63, I'm betting that you have come to understand that you are not your body, nor does it define who you are. I'll also wager that you have been in your body long enough to learn that it will do things to you that you would never have imagined, and that it rudely refuses to ask your permission. In short, that's what is going on here. Your body is doing something without your permission. You have nothing to be ashamed of or feel guilty about. Some of the guys here don't seem to understand that.
Hypogonadism (Low Testosterone) would seem to be a high probability for causing your gyne given my readings on the subject in learning about my own hormonal issues. Of course, there are several other possible causes and only your doctor can determine that. Gynecomastia is a symptom of other health issues and not a cause.
Anon