Category Archives: Dutasteride

Finasteride and Dutasteride AMA

Finasteride and Dutasteride Dosage and DHT Reduction
A comparison of DHT reduction via Finasteride and Dutasteride.

I first heard about Dr. Kyle Gillett of Gillett Health (Kansas) when watching the Huberman Lab Podcast on hair loss that he helped create earlier in 2023.

At the time, I had forgotten that Dr. Gillett gave me a detailed and somewhat complicated response to one of my past questions on Twitter in 2022:

Finasteride and Dutasteride AMA

This week, Dr. Kyle Gillett and his clinic’s nurse practitioner James O’Hara conducted a very interesting ask me anything (AMA) session on YouTube. They answered numerous questions in relation to both dutasteride (Avodart) and finasteride (Propecia).

Among the numerous subjects they discuss include: side effects; post-finasteride syndrome (PFS); systemic absorption; dosage iterations; topical finasteride; and topical dutasteride. They did not cover the finasteride and low-dose dutasteride combination treatment (that has become popular on Reddit) in detail.

However, Mr. O’Hara does state that he takes both drugs, and might have gotten some OCD exacerbating mental issues when being on finasteride alone. I have my doubts about such connections, but I am no medical expert.

I was pleasantly surprised to hear that both of these guys take oral dutasteride for their own hair loss and seem to prefer it to finasteride. Both have seen significant benefits to their scalp hair growth while on the drug. Make sure to read my past very important post on dutasteride hair loss reviews and the numerous subsequent reader comments and testimonials.

The reason I was surprised is because enlarged prostate (BPH) drug dutasteride was never approved to treat hair loss in the US by the FDA. In fact it is still only approved for the latter purpose in Japan and South Korea. So most US medical professionals tend to stick with the usually weaker finasteride. Moreover, almost no male US celebrity has ever admitted to taking dutasteride for his androgenetic alopecia. With a notable exception being Ashton Kutcher.

In contrast, quite a few have admitted to taking finasteride to treat their hair loss, including Donald Trump. Do note that finasteride seems to work over the long-term in most patients. However, dutasteride is often an even better option if you get no side effects. In the below video, the doctor and nurse discuss starting patients out on a low dose of dutasteride so as to slowly reduce dihydrotestosterone (DHT).

Interestingly, Dr. Gillett recently stopped taking dutasteride for some kind of fertility related reason. Maybe he is trying to have children? Right away, he saw a reduction in his scalp hair and an increase in his body hair. It is refreshing to see such a video based dutasteride and hair growth related testimonial from a medical expert. Mr. O’Hara said that he saw a reduction in his acne and sebum after starting 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.