I'm 24 and I have a large bald spot on the top of my head. Is there anyway to grow back my hair? (photo)

When I was in my teens I had a full head of hair and could hardly grow any facial hair(Since I was 20, I could grow facial hair). This all changed when I started losing weight quickly at around 19 by exercising a lot. At 18, I was approx. 185 lbs, now I am about 130ish and been that way for about 3 years. I have been noticing hair loss since I was 20. Has my losing of weight and the final stages of puberty have something to do with my dramatic hair loss? Can I regrow my hair or is it too late?