Finasteride is a progestin which does not convert to cortisol or metabolites like progesterone does. Since it does not convert to metabolites as progesterone it lowers NADPH. This takes down 5 alpha reductase. Also since progestin does not convert into cortisol, it puts pressure on cortisol and this weakly inhibits the enzyme that breaks down cortisol which is 5 beta reductase. Most of the symptoms while on fin are coming from inhibiting 5 beta reductase enzyme. the higher dosage of Fin , the more you inhibit this enzyme. and the higher cortisol goes.. 5 beta reductase is the enzyme which is responsible for bile acids. This is why progestins stop bile production. Actually progesterone in certain cases could do the same.
So while you are taking finasteride, you lower NADPH and you lower NADP , you stop 5alpha reductase and you stop 5 beta reductase. Most of the symptoms come from 5 beta reductase . And the higher fin dose the more you inhibit this enzyme. This is why if you found the optimal dosage not to inhibit this enzyme you would be only inhibiting 5 alpha reductase and would not have problems while on fin.
Now. After you come off fin. I assume. your NADPH production spikes back up really high. Since fin was blocking it. while you were on it. . This is why you see high DHT in some of the PFS guys. This high NADPH inhibits 5 beta reductase even further. Since 5 alpha reductase works on NADPH, but 5 beta reductase's end product is NADPH. SO when you come off fin, your NADPH production is high , and 5 beta gets inhibited even more. Your bile acids are zero now. your fat solubles are zero, and also your cortisol is high and aldo is high , since 5 beta reductase does not break them down. You are in alkalosis. and your fat digestion is zero.
So once again. When you are on fin , since fin raises metabolism but does not convert to cortisol like progesterone should have. It lowers both 5 alpha and 5 beta reductase.
But when you go off fin, this increases 5 alpha back to normal and beyond , but it totally inhibits 5 beta even more since NADPH decreases 5 beta
This is why andro works( inhibits 5 alpha) , 5 alpha inhibitors work, licorice works( increases cortisol) and this pushed 5 beta higher, dexamethasone , and progesterone. amino acids, zinc finger , RU lowers metabolism and increases cortisol and 5 beta increased . they all decrease need for cortisol and this increases 5 beta reductase.
So PFS is a imbalance between NADP and NADPH after you come off FIN. NADPH is what 5 alpha works on, and NADP is what 5 beta works on. NADPH is also made out of NADP. So this makes 5 beta and 5 alpha 2 enzymes that go opposite of each other. NADP to NADPH ratio. when NADP high 5 beta is higher, when NADPH is high , 5 beta is lower.
We will be trying many things to put 5 beta back online.
This is basically more precise explanation of the receptor theory but from enzymes view.
For those who are still taking fin, you can always adjust dosage so you dont inhibit 5 beta reductase too much , and this way you will be on fin with minimal sides . If you adjust the dosage lower, this will grow even more hair since you wont be experiencing protein wasting hairloss like in hyperthyroidism. Fin is just uncontrollable progesterone. Fin does not convert to cortisol, but causes the rise of metabolism. When metabolism rises progesterone converts to cortisol to make more sugar and aminos. But fin cant convert , and if you take too high of a dose it is like being hyperthyroid. Puts too much pressure on cortisol and closes down 5 beta reductase with bad sides coming from 5 beta reductase
IF you test your 5 beta reductase and make sure it is good, you can stay on fin without sides
For people who went off the fin .
@TubZy and I are trying different protocols to fix this situation more precise. But you have many ways to manipulate NADP NADPH ratio, knowing this mechanism that we outlined above
I hope this explains why people feel bad on anything that increases 5 alpha reductase.
and for those who still think what andro does - just look a this chart.
Hormonal Charts & Pathways
as you can see andro inhibits 5 alpha reductase. Because androstenedione converts to androsterone via 5 alpha reductase.
@mattyb