Hello James this question is for you. I was watching one of your videos on youtube today and realized that you have very healthy hair, at least much healthier than mine. I am a 29 year old man who has wanted to grow his hair out for sometime but the problem is that my hair comes out so coarse and dry that it looks bad. I have always had cold hands which lead me to beleive that I have hypothyroidism.

This is a very good possibility.  You can check your basal body temperature as a confirmation.

Could high DHT also be a cause?

DHT would cause the hair to fall out by affecting the hair follicles.

Last time that I tried growing my hair out I noticed that the hair on the sides and back of my head grew a lot faster than the hair on the top.

The slower growth can be from DHT.

Also, what do you personally do for your hair care routine? Do you use special shampoos or conditioners? It seems like any shampoo that I use results in very dry, puffy looking hair. Thanks a lot in advance.

I do not use anything special.  No special shampoos and rarely ever a conditioner.

Main things I do for my hair are never use hot water on my hair.  Hot water damages both the hair and skin.  I take warm, but not hot showers.  Secondly I almost never use a hair drier on my hair since again the heat is very damaging to the hair.

I do not like conditioners since they tend to gum up the hair with waxes.  If my hair is drying out I will sometimes add some palmarosa essential oil to my shampoo, which is a great hydrator or I will spritz my hair with a weak citric acid solution then brush it through with a boar bristle, not nylon, brush.  Nylon brushes create a lot of static electricity that also damages the hair.