Category Archives: Dutasteride

How Does Dutasteride Impact Testosterone and Estrogen Levels?

In 2015, I wrote a popular post on how finasteride impacts testosterone and estrogen levels. This time, I want to examine how the stronger DHT inhibitor dutasteride effects testosterone and estrogen levels.

Propecia (brand name finasteride) increased mean circulating levels of both testosterone and estradiol (estrogen) by approximately 15% per one study by its manufacturer Merck. See page 8 in here under the section on pharmacodynamics for more details. However, this increase is not substantial enough to cause testosterone and estrogen levels to exceed the reference range. In the same study, finasteride (1 mg) rapidly reduced serum DHT by 65% within 24 hours of ingestion.

Dutasteride, Testosterone and Estrogen

Dihydrotestosterone (DHT) blockers reduce the conversion of testosterone to dihydrotestosterone. This results in higher levels of circulating free testosterone (aka the male sex hormone).

When first researching this subject a few years ago, I expected that dutasteride would cause significantly greater increases in testosterone and estrogen levels in comparison to the weaker finasteride. Dutasteride inhibits DHT levels to a far greater extent than finasteride. Moreover, it inhibits both type 1 and type 2, 5α-reductase isoenzymes which are responsible for the conversion of testosterone to DHT.

See my post on dutasteride being more effective than finasteride when it comes to hair growth. Note that the former also causes higher rates of side effects in comparison to the latter. I take dutasteride (0.5 mg once every 3 days), and feel like it might have given me some weight gain and gynecomastia.

However, the one time I measured my estrogen (female sex hormone) level, it was within the normal range for a male. I also have a far more sedentary life than when I used to be extremely skinny (although my caloric intake has not changed). On a side note, estrogen can lead to increased hair growth.

Dutasteride and Testosterone

According to the package insert from GSK (the manufacturer of the original Avodart brand):

“In BPH patients treated with 0.5 mg of dutasteride daily the median decrease in DHT was 94% at 1 year and 93% at 2 years. The median increase in serum testosterone was 19% at both 1 and 2 years. This is an expected consequence of 5α-reductase inhibition and did not result in any known adverse events.”

According to the Avodart monograph from GSK, a 52 week treatment with dutasteride 0.5 mg/day resulted in:

No clinically significant change compared with placebo in sex hormone binding globulin, estradiol, luteinizing hormone, follicle-stimulating hormone, thyroxine (free T4), and dehydroepiandrosterone. Statistically significant mean increases compared with placebo were observed for total testosterone at 8 weeks and thyroid-stimulating hormone (TSH) at 52 weeks. The median percentage changes from baseline within the dutasteride group were 17.9% for testosterone at 8 weeks and 12.4% for TSH at 52 weeks.”

Dutasteride Testosterone
Dutasteride and testosterone increase. Source: American Journal of Men’s Health, Volume: 11, Issue: 1. Favaro et al.

The good news is that after stopping dutasteride for 24 weeks, the mean levels of testosterone and TSH returned to baseline. However, note that this study consisted of a very small sample size of just 26 volunteers. The FDA drug facts page on Avodart has the same information.

When it comes to testosterone, other studies also seem to indicate similar changes. For example, a 2010 South Korean study of 120 patients with benign prostatic hyperplasia (BPH) found that dutasteride increased serum testosterone levels around 16% after one year of treatment. A 2018 Japanese study of 110 BPH patients taking daily 0.5 mg dutasteride concluded a 20% increase in both total and free testosterone levels compared to baseline.

And a massive 2002 US study with 2,167 patients taking dutasteride found that they experienced a median increase in testosterone concentration of 19.7% from baseline at month 24. And this rose slightly to 21.9% at month 48

Conflicting Reports on Estrogen Changes

Dutasteride Estrogen
Dutasteride caused a slight increase in serum estradiol (estrogen) levels. Source: American Journal of Men’s Health, Volume: 11, Issue: 1. Favaro et al.

I find it hard to believe that finasteride can raise mean estrogen (or estradiol) levels by 15 percent, but the stronger dutasteride has a negligible impact. The latter conclusion per the GSK Avodart monograph that I linked to earlier.

I will update this post as I find more studies discussing the impact of the latter on estrogen levels in men. One study from Brazil (image on right) concluded that:

“There were no statistically significant alterations in the serum estradiol levels in the dutasteride group compared with the placebo group. But there was a slight increase in the serum estradiol levels in the dutasteride patients.”

A more recent 2020 study from Japan concluded that dutasteride increased estrogen levels by 9.4%. However, the results of this study were strange due to the fact that DHT levels only declined by around 40 percent rather than the expected 90 percent. The authors noted this anomaly versus the findings of other such past studies.

Dutasteride (Avodart) Reviews and Ratings

I will delete most comments that are unrelated to Dutasteride (Avodart). Post originally published in February 2015.

Update: June 2021 — New Dutasteride and Finasteride study sponsored by GlaxoSmithKline (GSK). Involved some esteemed scientists and advisors, including Dr. Manabu Ohyama.

“Dutasteride may be more potent than finasteride in modulating the expression levels of key hair growth genes (e.g. FGF7, IGF1 and WNT5a). This study provides supporting evidence that type I 5AR may be involved in hair growth in addition to type II 5AR”.

Update: February 2022 — A new study concludes that Dutasteride 0.5mg/day is the most effective male hair loss treatment.

Dutasteride (Avodart) for Hair Loss

Dutasteride for Hair Loss.
Dutasteride (Avodart) Capsules for Hair Loss.

I have written about Dutasteride (brand name Avodart) many times before on this blog. This drug was first approved by the FDA in 2002 to treat benign prostatic hyperplasia (enlarged prostates).

Dutasteride has not yet been officially approved to treat hair loss in the US or EU. However, it was approved for that purpose in South Korea in 2010, and in Japan in 2015.

It seems like GlaxoSmithKline (GSK) does not want to go through the approval process any more. They did do some clinical trials on Dutasteride and androgenetic alopecia. The results were published in 2018 and deemed a success.

In any event, the approval in South Korea and Japan is still a huge development. To date, only two drugs (Minoxidil in 1988 and Finasteride in 1997) have ever been approved by the US FDA to treat pattern hair loss. It has been almost 25 years since the last  US approval of a drug to treat male pattern hair loss!

Before and After Photos

Make sure to see some before and after photos of people taking Dutasteride to treat their hair loss. Some of those are in  people taking it in combination with Minoxidil. In the US, many people use  generic Dutasteride (or brand name Avodart) off-label to treat their hair loss. The most famous of these is Ashton Kutcher. Also see this favorable Avodart experience from Rick Rosner.

Hair Growth Prospects and Side Effects

Based on many existing studies and anecdotal evidence, it is virtually guaranteed that Dutasteride will result in superior hair growth/regrowth in comparison to Finasteride. However, the former will also result in higher rates of side effects compared to the latter. These higher rates of side effects are unlikely to be drastic enough for the FDA to deny GlaxoSmithKline permission to market Avodart for hair loss.

One 2013 article that reviewed numerous recent Finasteride and Dutasteride related studies suggests a 5-9 percent chance of erectile dysfunction. In most cases, such side effects are not permanent, although some people have seen permanent problems even after complete cessation of drug ingestion.

The big question is whether GSK will deem it worthwhile to produce and market Avodart for hair loss. Potential market and revenue prospects might not be sufficient enough to proceed. And they will also have to consider potential losses based on recent lawsuits against Merck regarding Propecia (Finasteride) side effects. Dutasteride will definitely have more people complaining of side effects in comparison to Finasteride.

Make sure to also see my posts on topical Dutasteride and topical Finasteride. Also of interest is the new trend of mesotherapy with Dutasteride for hair growth. Also known as Dutasteride injections.

Dutasteride for Hair Loss Reviews

In the meantime, rather than wait for the FDA and GSK, I have decided to write this post. I hope to see numerous comments from people who have tried to use Avodart to treat hair loss. Success and failure testimonials are both welcome.

By now, there must be well over 100,000 men around the world who have used Avodart off-label to try to regrow hair. When the drug was first approved in 2002 to treat enlarged prostates, people on online hair loss forums went berserk with excitement.

I hope to see many testimonials and comments to this post in the coming years. I will try to only allow specific comments and concerns related to the drug itself. Including opinions about side effects, cost (including the cost of generic Dutasteride), dosage and so forth.

I hope that this post and your helpful Avodart for hair loss reviews ends up becoming extremely useful. On hair loss forums: Dutasteride related testimonials are either not broken out in a separate subcategory; or swamped in number by Finasteride related posts.

It should also be noted that balding older men who have taken Avodart to treat their enlarge prostates have sometimes noticed hair regrowth in areas of their scalps that have been totally barren for many decades. You can read some of these encouraging testimonials in several of the below links.

Regrowing hair in totally bald scalps is extremely difficult and akin to a miracle with weak existing treatments. Even when effective, current hair loss treatments usually only maintain hair. At best, they regrow only recently lost hair.

Dutasteride (Avodart) Reviews: Links of Interest

Note: Dutasteride is not meant to be used by women who are planning to get pregnant.