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Finasteride and 5-beta Reductase

I stumbled upon an old comment on one of the articles here that presented a theory I haven't heard anywhere else. If this is correct, it could provide a way to get the benefits of finasteride/Propecia with much lower chance of side effects. Here's the comment:

Published analysis shows that [finasteride] DOES NOT act as an antagonist as thought but actually ACTS as a mechanism-based inactivator of the 5a Reductase Enzyme. This reaction throws off a bisubstrate analogue in which dihydrofinasteride is covalently bound to NADP+.

Subsequently through competitive activity Finasteride metabolates impact on the AKR1D1 enzyme (5b reductase) and in a dose dependant manner that is higher than the dose dependent value on the 5a Reductase.

So Finasteride blocks 5a synthesis and all the effects are as you say well documented.

Research now shows that in a dose dependent manner it blocks the 5b synthesis. Now this process has significant effects on sexual behaviour and brain activity, not least through 5b progesterone synthesis and it’s metabolates.

Personally I began on 1mg for 2 years and had all the side effects recorded: reduced watery ejaculate, reduced desire, reduced feelings, no dreams, dry eyes, etc (note 5b very important here). These reduced after 13 months, exactly as others see and was shown in tests. Hair grew remarkably, by as much as 30% by year 2, even to a full fringe (little benefit at 6 months, just steady increase to year end then big gain in 2nd year).

So I accepted side effects.

In year 3 Doctor gave me the full 5B report and I dropped to 0.5mg per day.

It’s now Year 6.

I have NO side effects at all and actually gained even more hair since year 2. The biggest changes have been in eyes (dryness eliminated and prescription actually improved from R-2.75 L-3.75 to R-2.25 L-3.50), sexual desire and mood (including regular dreams). Erectile performance and orgasm actually very good, would suggest higher than before start on Fin, driven by +12% Testosterone and +10% Estradiol compared to pre-Fin start (Doctor has done pre and post blood tests and one every 12 months).

I can only speak from.experience.
The article on Finasterides true working methods and impact in 5B Reductase can be found here….then Google the impact of 5B suppression and you will recognise I’m sure the effects…

Basically, he seems to be saying that finasteride lowers 5A reductase the same regardless of dose, but that 5B reductase is dose-sensitive and that it's this that causes side effects. Does anyone have any insights on this?