Hi mate.
You don't want to reduce your DHT levels bro.
DHT is responsible for strength gain, muscle hardness, fat loss, sex drive, recovery.
If you are very worried about hairloss, then you have to make a choice. Either you want good gains, or you want to keep your hair for a couple more years. If you are going to lose your hair, you can not stop it. You can delay it slightly. If you want to keep your hair then do not take any AAS. If you want good gains then forget the hair. Sorry bro, but some people are just destined to go bald.
Hope this helps bro.