I've already written about if Finasteride lowers Testosterone levels.
I felt an article on Dutasteride was justified as well.
If you read the Finasteride article, you already know that Finasteride does not lower Testosterone, which is a common misconception.
It actually increases Testosterone levels, as does Dutasteride.
Dutasteride increases Testosterone levels to an even greater extent than Finasteride.
How 5-Alpha-Reductase Inhibitors Increase Testosterone And Estrogen Levels
Once daily dosing of Propecia (Finasteride) will increase Testosterone and Estrogen levels in the body by about 15%.
The reason for that is when Testosterone hits 5-alpha reductase, you now have a blockage between Testosterone being converted into DHT.
Testosterone that would have otherwise converted to DHT remains as Testosterone.
Now, you actually have more Testosterone than you would have otherwise.
In turn, you also now have more Testosterone that will aromatize into Estrogen.
The net result of that is a 15% increase in Testosterone and Estrogen.
A common question is if Dutasteride does the same thing, and how much would Dutasteride increase Testosterone if it has the same mechanism of action.
If you're inhibiting 5-alpha reductase more with Dutasteride than you would be with Finasteride, logically you would think, “okay, well that's going to increase Testosterone even more.”
You would be correct to assume so.
The Avodart highlights of prescribing information outline exactly how much Dutasteride increases Testosterone by and decreases serum DHT levels [R].
Dutasteride Effect On Serum DHT And Testosterone Levels
The maximum effect of daily doses of Dutasteride and the reduction of DHT with subsequent increase in Testosterone is dose dependent and observed within one to two weeks.
After two weeks of daily use, 0.5 mg of Dutasteride lowered serum DHT levels by 85% at the end of week one, and 90% at the end of week two.
After one year, DHT levels had decreased by 94%.
After fully being saturated in the body Dutasteride inhibits serum DHT by about 93 to 95%.
The median increase in serum Testosterone for these same patients with those reductions in DHT was 19% at both one and two years 26% at three years and 22% at four years, but the mean and median levels remained within the physiological range.
What that means is compared to Finasteride, Dutasteride will increase your Testosterone by approximately 4 to 11 more percent (this is based on a 0.5 mg Dutasteride dose and will vary at other dosages).
Finasteride increases Testosterone by 15% and Dutasteride increases serum Testosterone concentrations by 19 to 26%.
The following graph from the study “The importance of dual 5a-reductase inhibition in the treatment of male pattern hair loss: Results of a randomized placebo-controlled study of dutasteride versus finasteride” outlines the evaluation of various dosages of Dutasteride in comparison to 5 mg of Finasteride and provides some very insightful data that is often not referred to in the hair loss community.
I will be delving into this study further in the next subsection of this article.
Before moving on, it should be noted that Dutasteride doesn't increase serum Testosterone levels significantly more than Finasteride, but it's notable.
Scalp DHT Reduction And Subsequent Increase In Scalp Testosterone Concentrations
I would be remiss to not mention the concurrent increase in scalp Testosterone concentrations that occur with Finasteride and Dutasteride use.
Most get too tied up in the serum level changes of Testosterone and DHT to take note of Testosterone and DHT concentrations literally where we care about it the most…
While most individuals will experience improved hair loss prevention outcomes with Dutasteride use relative to Finasteride, there are a minority of individuals who actually accelerate their hair loss with Dutasteride monotherapy (me included).
It also explains why some individuals with aggressive hair loss don't experience any relief with 5-alpha reductase inhibitor use.
Scalp DHT concentrations in the Dutasteride groups were significantly suppressed compared with placebo in a dose-related manner.
As with serum DHT, the 0.1-mg Dutasteride and 5 mg Finasteride groups showed a comparable degree of scalp DHT suppression (32% and 41%, respectively).
Yes, you read that correctly.
5 mg of Finasteride only lowers scalp DHT by 41% (5 times the dosage prescribed for hair loss).
That's what's actually occurring despite most believing they have 70% of their DHT being wiped out with 1 mg per day.
Scalp DHT decreased by 51% with 0.5-mg Dutasteride and by 79% with 2.5-mg Dutasteride.
Scalp testosterone levels significantly increased in all active treatment groups compared with placebo, increasing by 23%, 39%, 99%, and 222% with 0.05-, 0.1-, 0.5 and 2.5-mg Dutasteride, respectively, and 23% with Finasteride.
The relationship between the mean percentage change in scalp DHT and mean change in hair count is shown in the image below.
As you can see, the efficacy of 0.1 mg of Dutasteride was roughly equivalent to that of 5 mg of Finasteride for hair loss prevention, with the 0.5 mg and 2.5 mg dosages outperforming Finasteride in efficacy measures.
For most individuals, Dutasteride is more effective at preventing hair loss, purely based on DHT suppression.
However, you should know by now that DHT isn't the only androgen that can cause hair follicle miniaturization.
Testosterone will still wreak havoc, just to a lesser extent than DHT.
5 mg of Finasteride resulted in a 23% increase in scalp Testosterone levels with a concurrent 41% suppression of scalp DHT levels.
0.1 mg of Dutasteride resulted in a 39% increase in scalp Testosterone levels with a concurrent 32% suppression of scalp DHT levels.
We can see based on this data that Finasteride actually is more efficacious at certain dosages, the problem with it is that it is so weak in comparison to Dutasteride.
Ideally, we want as much DHT suppression as possible with no concurrent boosting of scalp Testosterone levels.
This is why some individuals actually regress when they switch from Finasteride to Dutasteride.
Their DHT is further suppressed, but their scalp Testosterone levels sky rocket and cause miniaturization that would've otherwise not occurred as dramatically had they just stayed on Finasteride.
0.5 mg Dutasteride is the daily dose most commonly used for hair loss prevention, and that dosage increases scalp Testosterone levels by 99%.
I assure you, cranking your scalp Testosterone through the roof is not a good thing.
In the following study assessing Testosterone's androgenicity irrespective of 5-alpha reduction to DHT it was determined that “These results demonstrate that if the prostatic testosterone content is elevated to sufficient levels, androgenic effects are induced without a requirement for an elevation in prostatic DHT content. Thus, the conversion of testosterone to DHT appears to function as a means of amplifying androgenic stimulation in the prostate” [R].
With that being said, when it comes to a trade off of suppressing 51% of scalp DHT for a 99% increase in scalp Testosterone, the net result will often be less hair loss for most individuals simply due to the high binding affinity and androgenicity of DHT relative to Testosterone.
However, in individuals with aggressive male pattern baldness, this may actually shoot them in the foot and cause an even greater acceleration of hair loss if their Dutasteride use was not accompanied by a topical or systemic anti-androgen with a high enough binding affinity to antagonize Testosterone at the Androgen Receptor.
For many, RU58841 sufficiently accomplishes this and cleans up the mess so to speak.
For some though, having 49% of their scalp DHT left in tact with a concurrent 99% boost in scalp Testosterone and trying to combat it all with a topical anti-androgen with a very short half-life and applying it in a suboptimal manner/frequency is not going to relieve them of their continued miniaturization.
I will delve into this topic further in future articles, but to the extent of how much Dutasteride will increase serum Testosterone and scalp Testosterone levels, the statistics outlined above are what you need to know and take into consideration when designing a hair loss prevention protocol.