Tren is used by Veterinarians, it was never made for human injection. Unlike those drugs like testosterone, anadrol, anavar etc for treatment of specific muscular distrophys that come along with radiation therapy or HIV/Aids or rare muscular diseases.
Tren is great, but if you do not use Testosterone with it, you will plumet your test levels and feel like ****. Test + Tren = you will want to bang anything you see.
Testosterone is relativity safe on the liver, less harsh than any Oral steroid that is, since it is 1) inject 2) doesn't have to be highly metabolized by the liver thus putting less stress on it. A night of binge drinking puts a heavier strain on theliver than using test. Tren however, well thats a different story. That puts a large strain on your liver, but nothing that is not reversable in low doses. However, I've had a few friends turn yellow from tren and some end up with liver issues with Methyl-tren but once they hopped off they were fine.
A lot of studies actually show testosterone being neuroprotective to, If i can dig up the study ill post it. But it was damn cool to see that long term of a study done on TRT patients.