I won't pretend I'm an expert on this

This is how it was explained to me, I'm still not sure about the science but I've seen a lot of people saying don't use them together.
Pasted
Both Testosterone and Nandrolone are effected by 5-alpha reductase enzyme, which changes Testosterone to Dihydrotestosteron(DHT) and Nandrolone to Dihydronandrolone(DHN). DHT is much more androgenic then Testosterone, in scalp and prostate, and by binding to receptor sites in hair follicules, causes hairloss. On a contrary, DHN is much less androgenic in same organs, and is, probably, the least androgenic of all steroids, while it keeps its anabolic properties.
Finasteride(Proscar, Propecia) is 5-alpha reductase inhibitor, meaning, it binds to the enzyme and prevent it from effecting the hormone(steroid)
In case of Testosterone, it's good, because it's preventing milder steroid from conversion to more harmful one.
In case of Nandrolone, it's bad, because it prevents stronger androgen from conversion to weaker one
Clear as mud?.....good
