Caffeine shampoo will add volume to your existing hair. Also, there is no shampoo that will impact on your T levels.
However, you may also need to assess the longer term damage the drug has done to hair follicles, which atrophy over time. Once they reach that stage, they are physically unable to regrow hair even if your body chemistry has changed. Some professional input may help you here. Other stimulants like laser combs, even scalp massage may assist in your case, although I know many experts doubt their efficacy.