Is there a good procedure to prevent hair loss on the crown of the head?

As I get older, when I look at the crown of my head under the light, my hair seems to have thinned a bit, and it feels like the top of my head is looking sparse!
So, it doesn't seem like I've completely lost my hair yet, but I want to prevent it in advance.

Are there any effective treatments to prevent hair loss on the crown of the head, or aside from treatments, are there any shampoos or medications available?

Which of the two would be more effective in helping with prevention?

Hair loss is really sad.