Here are some of my thoughts on this. I’m still learning myself.
Finasteride is administered to suppress your 5 alpha reductace enzyme from converting testosterone to DHT. It’s an 5AR inhibitor.
The 5AR enzyme also converts other hormones as well that if inhibited, will also slow down conversion.
For exogenous test only, this is great as it will help block a lot of that conversion to DHT within the body.
For other compounds like 19nor or DHT derivatives, it definitely works in a different way.
It doesn’t seem to help if you are administering DHT derivative as they compound won’t interact with 5AR like testosterone does. With that said though, DHT derivatives may be a little healthier on the hairline or other androgenic side effects as they were derived from DHT, but changed slightly to help lesson those side effects. I know that is just the theory at least, and many have had androgenic side effects like hair loss with something like masteron.
When it comes to say, nandrolone, 5AR helps convert that in the body to DHN, which is very low on the androgenic scale. With 5AR being inhibited from finasteride, that conversion will not happen as effectively, building up nandrolone in the system just as it would testosterone without 5AR enzyme to convert to DHT (or maybe greater increase in estrogen on the test side of things)
Now my question with this, has been for a while. Even though nandrolone is allegedly way more androgenic than its 5AR converted hormone DHN, is Nandrolone MORE androgenic than DHT or testosterone in a way to cause GREATER side effects?
Like, if you stop using finasteride to convert nandrolone to DHN, will you have the bigger problem (excess DHT from your testosterone) due to no inhibition of 5AR?