Proviron (Mesterolone) is the closest thing we have to orally active Dihydrotestosterone (DHT). It’s basically methylated (1-methyl) DHT. As a result, Proviron is not capable of being metabolized (aromatized) to estrogen, and is also not progestenic. It’s actually pretty light on the liver, and not very toxic at all, as it is not c17-Alpha-Alkylated, but rather is 1-methylated. And of course, being a DHT-based compound, this stuff isn't going to be great for female athletes to use in high doses, although from interviews with females, 12.5-25mgs a day seems to be very tolerable. Virilization (development of male sexual characteristics) is going to be a concern for women daring enough to try this stuff at high doses.
Proviron is typically thought of as a hardening agent, and as being not very anabolic on its own. I don’t know of too many men who use it at anything resembling high doses, but personally I’d love to see what it can do at a 50-100mg/day dose- essentially, that’s the dose range we see orally administered DHT compounds being used at, for an anabolic effect. At 25mgs/day it’s going to function as a bit of an anti-estrogen and a libido booster, but probably won’t be building much muscle.
A very interesting fact about Proviron is that it binds very well to SHBG (Sex Hormone Binding Globulin) which is the transport hormone responsible for reducing the amount of circulating free testosterone in your body.(1) It actually binds to SHBG better than almost any other anabolic steroid that I’m aware of. Proviron also binds to the Anabolic Receptor (AR) better than any commercially available oral anabolic .(1) While the previous two effects are certainly desirable effects, this oral version of DHT also has a very high affinity for binding to receptors in the scalp and prostate, causing some possible nasty side effects, like male pattern baldness and prostate enlargement.
So what we have here is a steroid which can possibly make other steroids more effective by inhibiting SHBG from attaching to them, and also has the additional benefit of reducing the amount of overall estrogen in the body. It’s not the kind of steroid that we can base a cycle around, but I think that those properties certainly make it beneficial for adding it into virtually any cycle. This of course also provides a hard, quality look to muscle that’s gained on a cycle, and an overall improvement in the look of the physique. Also, up to 100-150mgs/day it has no depressing effect on low to normal serum FSH and LH levels (2). In fact, if your natural hormonal levels are depressed, it may even be able to raise LH (3), which can then raise your natural testosterone levels.
So Proviron is very synergistic, but what I’ve found from interviews with people as well as in studies, it’s not very effective on it’s own.(4)
Although the genuine, brand name “Proviron” is not found frequently on the Black and many Underground Labs don't even produce it, it’s available as a paper anabolic, at a reasonably inexpensive cost.
References:
1. Relative binding affinity of anabolic-androgenic steroids: comparison of the binding to the androgen receptors in skeletal muscle and in prostate, as well as to sex hormone-binding globulin.Endocrinology. 1984 Jun;114(6):2100-6.
2. The effect of mesterolone on sperm count, on serum follicle stimulating hormone, luteinizing hormone, plasma testosterone and outcome in idiopathic oligospermic men.Int J Gynaecol Obstet. 1988 Feb;26(1):121-8
3. The effects of mesterolone, a male sex hormone in depressed patients (a double blind controlled study). Methods Find Exp Clin Pharmacol. 1984 Jun;6(6):331-7.
4. [Androgen substitution in the andrological disease picture] Andrologia. 1983 May-Jun;15(3):283-6. German.