If you're 19 and seeing signs of genetic hair loss, my advice to you is to free your mind of concern about it, and enjoy what hair you have - while you have it!
I'm 33 now, and I noticed the first signs at 19 also. I thought it was the end of the fucking world. By my mid-20's, it was worse. By my late 20's, worse yet. Now, in retrospect, I realize my hair was really fine from 19-25. I wish I would have not concerned myself about it then.
Right from 19, and along the way, I tried every damn thing - to the fullest extent & religiously. The bottom line is that it is all shit. The best of them had only moderate results THAT DON'T LAST. You have to use the stuff forever, and even if you do, you build up a tolerance so the effectiveness drops way off. And even when they work at their best, they do not give you what you are looking for in your early 20's (hair as full as your good hair). I sure wish it weren't true, but it is all a waste of time & money. If you are gonna use anything in your early 20's, try the cosmetic products (masking/coverups) like couvre or cover-up. (no, I don't work for them). Or even creative use of hair-gel.
As for me, my hair is now 50% gone, so I just shave it. It's a big pain. Plus, I have to make sure my head stays fairly tan so I don't look like cue-ball. The only thing I would consider now other than shaving is a quality hair system. I don't care to blow the cash on it now. Yes, I'm still a little bitter about it. I still feel going bald so early robbed me of my youth, and distanced me (in appearance) from my peer-group. But if you're 19, enjoy now! It's managable now - you'll have plently of time to be pissed about it in your late 20s.
bonapart