You can always just admit to tackling your hair problem because it bothered you and not get specific about what you've done.
When asked, you just say that there are tons of new products & drugs on the market, you've tried them and they seem to be working.
99% of your friends will accept that.
If your hair looks good, they'll even applaud you for it.
The ones that will want to know more details will be other guys worried about their thinning hair!
You can decide what you tell them on an individual basis.