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Why bother to add dutasteride to your testosterone cycle?

Chemical athletes who are worried about their prostate sometimes combine testosterone with substances like finasteride or dutasteride. According to the results of the trial that Shalender Bhasin published recently in JAMA, this strategy has no negative effects. But it doesn't have any positive effects either.

Finasteride [structure shown below right] and its more effective little brother dutasteride [structure left below] are steroids. They block the enzyme 5-alpha-reductase, thus preventing the formation of DHT. If you take 0.5 mg dutasteride every day, you'll block DHT formation by about 95 percent.

Doctors wonder whether it's worth given men at risk of prostate cancer 5-alpha-reductase inhibitors. Dutasteride could reduce the likelihood of developing the disease by a quarter. [Engl J Med. 2010 Apr 1; 362(13): 1192-202.]

Why bother to add dutasteride to your testosterone cycle?

On the other hand, researchers are wary of side effects of substances like finasteride and dutasteride. If you block DHT formation, do you also reduce muscle mass?

Why bother to add dutasteride to your testosterone cycle?
Maybe you don't, because the binding hormone SHBG draws most of the DHT molecules out of the bloodstream before they can stimulate muscle growth. But maybe you do, because in test tubes DHT is a more powerful androgen than testosterone.

Bhasin and his colleagues stopped testosterone production in 140 men aged 18-50 by giving them leuprolide. Then they divided the men into eight groups. Four groups were given a weekly injection of 50, 125, 300 or 600 mg testosterone-enanthate for 20 weeks and took a placebo every day. Four other groups were given the same amount of testosterone and took 2.5 mg dutasteride every day.

Dutasteride didn't reduce the increase in lean body mass in the men who took higher doses of testosterone. It didn't inhibit the reduction in fat tissue either.

The administration of the higher testosterone doses boosted the power the men developed when doing chest and leg presses. Dutasteride didn't lower the increase in strength in these groups.

Why bother to add dutasteride to your testosterone cycle?

The addition of dutasteride had no effect on the testosterone level, but it did have an effect on the DHT level. There were no effects on sexuality. Dutasteride had no effect on the prostate either.

Why bother to add dutasteride to your testosterone cycle?

In this group the addition of dutasteride had neither positive nor negative effects. On the basis of these results you may well wonder whether DHT really is the bad guy when it comes to the prostate, but the researchers don't draw this conclusion. On the contrary, they suggest: if DHT inhibitors have no effect on the prostate, then testosterone may be just as bad for the prostate as DHT.

Pharmacologists are experimenting at the moment with SARMs non-steroid compounds that don't convert into DHT, but do have positive effects on muscles, bones and sexual performance, via the androgen receptor. Scientists hope that these are safer than classical anabolic steroids.

The JAMA study suggests that SARMs are not as safe as pharmacists had hoped, the researchers sigh. "While our data suggest that SARMs that do not undergo 5-alpha reduction can exert anabolic effects on the muscle, they also indicate that such a strategy may not necessarily be effective in sparing the prostate, depending upon androgen dose. The prostate safety of such SARMs will need careful scrutiny."

JAMA. 2012 Mar 7;307(9):931-9.

Nandrolone finasteride combination increases androgenic side effects, not more effective 28.08.2011
Testosterone enanthate works just as well when you take finasteride too 06.06.2010
Combined with DHT blocker testosterone is still anabolic 08.12.2009