What are some good hair loss prevention shampoos?

I thought I was bald before, so I shaved my head a week ago to see what they look like (16 years, btw). runs good I have very thick hair (hair individual essays, counting the hair I mean). I never noticed more than one or two hair falling out when in the shower. I also tried to pull her hair, and only occasionally would a hair would come out. But anyway now to the question. I was wondering if there are shampoos out there that were really good for slowing down hair loss? Not sure if shampoo with DHT blockers (the scalp) can be used by people of 18 years. I’m seeing a dermatologist next week or two so I ask him as well.