Category Archives: Estradiol

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 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. 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.

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.

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.

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

“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 15-16 percent after one year of treatment. A 2018 Japanese study concluded a 20 percent increase in both total and free testosterone levels.

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. 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.

Estrogen Therapy and Hair Growth

For the male readers of this blog, estrogen (also known as oestrogen) is not something that one would consider to be of interest. For one, estrogen is largely a female sex hormone. What male would want to start taking estrogen and develop female secondary sexual characteristics such as breast enlargement?

Having said that, estrogen does have some properties that benefit overall health. Among these include heart protection (less atherosclerosis); strengthening of immunity; and reduction of inflammation. High levels of estrogen are though to be one of the reasons behind why females outlive males. The main negative of  high estrogen is a greater chance of developing breast cancer.

Update: December 24, 2021

Estrogen Monotherapy for Hair Growth

Since I originally wrote this post, I have become increasingly fascinated by estrogen’s hair growth properties. In my 2021 updated post on Male-to-Female (MTF) transgender persons, some of the before and after transformations are astounding.

Most transgender females take estrogen (typically in the form of estradiol, aka “E2”) as well as Finasteride or Dutasteride. Many also add anti-androgens such as spironolactone or cyproterone acetate into the mix. This is known as hormone replacement therapy (HRT).

What I am most curious about is non-transgender men who only use topical estrogen (cream, lotion, patch or spray) to regrow their hair. I would have never though that this would be a very effective solo hair loss treatment. Moreover, some amount of topical medication always gets absorbed into the bloodstream. So the feminizing side effects are likely to be significant, even if perhaps less so than with injected or oral estrogen supplementation.

Reddit to the Rescue

What encouraged me to re-examine subject matter is Reddit. In recent months, I have seen a number of threads by people focused on using estrogen monotherapy to treat hair loss. In many cases, the “monotherapy” is ultimately supplemented with Minoxidil or Finasteride, but this is still okay by me.

I do not frequent Reddit more than twice a week, and rarely go to the transgender related subreddits. So I likely missed dozens of  other threads in 2021. Thankfully, I bookmarked the below ones. I hope to ultimately find more such testimonials from males who are definitely not transgender. In the comments, feel free to post links to any that you find interesting. And they need not just be limited to Reddit.

  • Yesterday, someone posted a question titled “Can estradiol mono-therapy help grow back your hairline”? Several of the responses are quite encouraging.
  • Three days ago, someone posted this amazing transformation from using just Finasteride and Oestrogel for two years. She claims that this is all her real hair.
  • One month ago, someone posted a very interestingly titled thread with six before and after photos (make sure to swipe right of each image). According to this person’s theory, an artificial selective estrogen receptor modulator (SERM) would be almost as good as a hair loss cure. Provided it is combined with an oral Minoxidil and an anti-androgen. Note that most people prefer an anti-androgen and DHT blocker combination. But oral Minoxidil is becoming a lot more popular too.
  • Earlier in 2021, someone posted phenomenal before and after results from using just estrogen plus Minoxidil as a hair loss treatment. I would guess that the vast majority of this transformation is due to the estrogen.

February 25, 2015

Estrogen Hormone Therapy and Hair Growth

The reason I decided to write a post on estrogen is because I recently read an extremely interesting 2012 interview with Dr. George Cotsarelis. While the main part of the interview is devoted to the oft discussed PGD2, there are several other interesting subjects discussed. The second page of the interview is what really surprised me in a good way.

In the first part of this interview, Dr. Cotsarelis discusses the old and well known Dr. James Hamilton study from the 1950s. In this research, it was found that men who were castrated before puberty (eunuchs) never went bald. However, upon being given testosterone, those with a family history of baldness still started to loose hair.

The second part of the interview is more interesting. It covers the fact that even after someone has lost much of his hair due to androgenic alopecia, he can regrow a lot of it when given estrogen (after castration)!

This point is supposedly verified by many studies on Male-to-Female (MTF) transitioning transgender persons. Such patients show hair regrowth after their being castrated and getting on estrogen hormone replacement therapy (HRT). Usually with the addition of an anti-androgen such as Spironolactone.

While I do not think any of us men want to get castrated or take estrogen (estradiol), this is still an incredible finding. One of the best examples is in the before and after image below from this study.

Estrogen Treatment Hair Growth
Estrogen (Estradiol) Treatment Hair Regrowth. Source: Journal of the American Academy of Dermatology.

Note that both estrogen and progesterone extend the anagen growth phase cycle of hair follicles. In contrast, testosterone and dihydrotestosterone (DHT) do the opposite and shorter the hair growth phase. Make sure to also read my post on how finasteride impacts testosterone and estrogen levels.

Hair Regrowth Difficulties

Over the years, I have read a number of articles in which doctors and professionals seem to suggest that once hair is gone (turns vellus), it can never return. This is also why Finasteride and Minoxidil virtually never bring back any significant amount of hair for someone who is mostly or entirely bald. However, it seems like hair can regrow in fully bald areas of the scalp in some instances.

There have been anecdotal reviews on Dutasteride actually regrowing long dormant hair. But these have been few and far between. Over a decade ago, Dr. Marty Sawaya caused an insane level of excitement on hair loss forums when she reported that one of her older patients gained back most of his lost hair when on Dutasteride. But that whole episode was controversial and not replicated.

More recent research suggests that a balding scalp still has all the follicle stem cells intact. But certain progenitor cells have become depleted. Basically, the cells are there, but the activity is not there. Dr. Cotsarelis has suggested that perhaps blocking PGD2 will allow the stem cells to make progenitor cells again. However, this is not a certainty, and neither is hair regrowth guaranteed once PGD2 is inhibited.

I suspect that this powerful impact of estrogen on hair regrowth is still not strong enough to grow back all of one’s lost hair. This is because many older balding MTF transsexuals seem to get hair transplants even after getting castrated and beginning estrogen therapy.

Finally, for men who take Finasteride (Propecia, Proscar), one potential side effect is increased estrogen levels. This sometimes results in the dreaded gynecomastia (male breast enlargement), along with fat gain in other parts of the body. Their are numerous complaints on hair loss forums about this side effect. Most studies indicate that the chances of developing gyno from taking 5-alpha-reductase inhibitors is extremely low.