Bill Roberts in "Enzymatic conversion of Anabolic-Androgenic Steroids":
"5alpha-reductase
This enzyme can do one thing and one thing only: convert a steroid with a double bond between carbon 4 and carbon 5 to one with a single bond between them (and also adding a hydrogen to each carbon so the total number of bonds remains correct.)
This means that it can convert testosterone to DHT (Figure 8) or nandrolone to DHN (Figure 9) but it cannot convert Winstrol or Anadrol (Figure 2) despite the uninformed claims of careless steroid authors. And although Dianabol does have a double bond between carbons 4 and 5, it nonetheless also is not converted by 5AR.
Both Type 1 and Type 2 versions (isozymes) of 5AR exist. Type 2 is present in the prostate, and Proscar is a good inhibitor of that isozyme. Type 1 is present in the scalp and skin, and unfortunately Proscar is a poor inhibitor for that type"
So, according to Bill, only Testosteron users can benefit from Finasteride, and will get worse hairloss if they use Deca.
Winstrol, Anadrol, Dianabol(obviously EQ), and I, personally believe Trenbolone also, are not effected by 5-alpha reductase enzyme, meaning that it doesn't really matter from the hairloss point of view, if you use Finasteride with them, or not.