finfighter said:
Dutasteride inhibits about 90%+ of DHT, and Finasteride inhibits between 60%-70% I would say that's more than a little bit of suppression....
In case of dutasteride, it's a lot.
In the early trials and clinical experience with proscar (this have had to be in the seventies) it was presumed by some researchers and doctors that impotence, lack of libido and not to mention INFERTILITY not only was possible SIDE effects, but would in fact be ADDITIONAL effects to shrinking the prostate.
The results turned out to be quite unexpected: only 2-4% suffered from side effects, the most common being lack of libido. Fertility seemed to be unaffected, and impotence was rarer than loss of libido. Another unusual finding was that prostate size shrinked allright, but not SO MUCH as one would expect.
This suggested several things: first of all, that prostate growth is affected by other substances than DHT (IGF, for instance, as researchers later figured out)
AND (most importantly):
*That testosterone BY ITSELF can stimulate the androgen receptor WITHOUT being reduced by alpha reductase
*That testosterone (and not DHT) play a greater role in libido and fertility than first thought
*That DHT in many men is produced "in excess"- we apparently have more than we use- or to put it more correctly: ALPHA REDUCTASE ENZYMES are present in excess in various tissues (not just skin and prostate), locally converting testosterone to DHT, and that this excess presence is contributing to BPH, prostate cancer and (surprise, surprise) BALDNESS in susceptible men.
This is why finasteride has an evident ANDROGEN INHIBITING- effect, and NOT an ANTI ANDROGEN- effect.
Of course later research have discovered that there's a reason for "excess" alpha reductase enzymes: bone growth and neuroendocrine function being two important factors. I'm sure more is to be discovered in the future.
Still; every piece of evidence suggest that FOR MOST MEN (though not all) finasteride is safe, and apparently safe for long time use.
Dutasteride hasn't been around for that long, but strangely enough, even though it inhibits both alpha reductase inhibitors, and decreases DHT by a heck of a lot more (90% vs 65%) IT STILL DOESN'T PRODUCE MORE SIDE EFFECTS.
It's weird, but those are the data.