Minoxidil: Does it actually work for hair regrowth?

So my brother’s been on this stuff for basically a year now and honestly, you can totally see the hair actually growing back in those bald spots, which is wild, but the catch is that once you stop using it, the growth just quits on you too.

My own hair has thinned out a little bit—nothing super crazy yet, but I’m definitely feeling it—so I was thinking about jumping on some Minoxidil just to get ahead of the game and stop the shedding before it gets bad.

Does anyone know if Minoxidil actually does anything to the healthy hair I've already got left?