Category Archives: Estrogen

How does Finasteride Impact Testosterone and Estrogen Levels?

Ever since I first started taking Finasteride a decade ago (with several stops and restarts in between), I have always been wary of side effects.  I therefore decided to be cautious and take around half the recommend dose (i.e., 1.25 mg once every two days instead of 1 mg every day).  There are numerous people who take 5 mg (!) of Finasteride per day for enlarged prostates and they generally seem to get limited to no side effects based on various studies, so perhaps I am overly cautious.  At the same time, there are also many hair loss sufferers who have taken 1 mg per day and complain about persistent side effects even after stopping the medication. However, as a percent of all people who take Finasteride, this number is tiny. Nevertheless, it still makes me err on the side of caution.  Recently, I tried to find out exactly how Finasteride impacts estrogen and testosterone levels in men.

Finasteride and Estrogen

Finasteride raises estrogen (the female hormone) levels, and this tends to be the number one concern of people taking the drug. Higher levels of estrogen in men can result in feminizing effects such as gynecomastia and increased body fat levels, along with sexual problems.  For years, I was curious as to how much estrogen levels go up by in men who are on Finasteride.  Do they go up to levels found in women (that would be scary)?  What are the typical estrogen levels in men and in women? After spending a good amount of time, I finally found an official brochure from the manufacturer of Propecia, Merck, that states that “mean circulating levels of testosterone and estradiol were increased by approximately 15%“. Estradiol = Estrogen (see next paragraph).  However, now I needed to find out how that compares to estrogen levels found in women.

There are three types of naturally occurring estrogens in women: estrone (E1), estradiol (E2) and estriol (E3).  Estradiol is the most important estrogen in non-pregnant females prior to menopause, estriol is the most important one in pregnant females, and estrone if the most important one after menopause.  Estradiol is the most potent of these three estrogens.

Blood tests for estrogen generally look at estradiol levels.  Men’s estradiol levels range from 15-60 pg/ml over the course of their lifetimes.  For women, the range varies significantly throughout their life, including during each menstrual cycle.  A female’s lifetime estradiol range is from 20-400 pg/ml, with post-menopausal levels being similar to those in men.  Various sources I checked show slightly different estimates for the above ranges, but in general, women have significantly more estradiol then men prior to menopause. It should be noted that while women’s estrogen levels are primarily manufactured by the ovaries, men’s levels are attained via the aromatase reaction that converts testosterone to estrogen.

From the above numbers, one can deduce that in young adult males, Finasteride will result in estradiol levels rising from say around 35 pg/ml to around 40 pg/ml (i.e., 15 percent increase). This finding makes me a bit more comfortable in continuing to take Finasteride.  I also vaguely remember taking a blood test in the past in which one of the measurements was for prolactin, and my levels were normal despite my taking Finasteride 1.25 mg every two days at the time. Abnormal levels of prolactin indicate that something is wrong with your testosterone and/or estrogen levels (for both men and women).

Finasteride and Testosterone

Finasteride reduces the conversion of testosterone to dihydrotestosterone (DHT), resulting in higher levels of circulating testosterone.  According to the earlier mentioned Merck brochure on Propecia, Finasteride also increases circulating testosterone levels by 15%.  Considering that men start to lose testosterone levels starting in their 20s, this is perhaps not such a bad thing.  In fact an increasing number of older people take testosterone supplementation, and the most famous example is the incredible 77 year old Dr. Jeffry Life.  I am very surprised that this man is still alive despite injecting himself with testosterone at a relatively old age. Also see Dr. Life’s before and after photos.

Note that testosterone supplementation is a very controversial subject, and I would not try it.  High levels of testosterone are linked to death from heart attacks.  I also think I am getting more adult acne due to taking Finasteride, although I am not 100 percent certain about that.  Many hair loss forum members have wondered if the slight increase in testosterone when on Finasteride helps one gain a bit more muscle mass when working out.  Also see this page for ranges on average and free testosterone levels in men and women.

Testosterone to Estrogen Ratio

While the 15 percent rise in circulating testosterone and estrogen levels in men taking Finasteride 1mg per day does not seem much to me, it is important to also watch out for the testosterone to estrogen ratio in case you ever get blood tests done.  It is quite possible that some people will see a significantly higher increase in circulating testosterone than in circulating estrogen (or vice versa) when on Finasteride, and the change in this ratio can have a big impact on your side effects.  Various reports suggest that when the testosterone to estrogen ratio changes significantly, one can often get unexpected side effects.


Numerous reports I have read seem to suggest that women’s higher levels of estrogens protect them to some extent from various serious medical problems such as heart disease.  While higher estrogen levels in women also mean substantially higher rates of breast cancer in comparison to men, in general, estrogen has more pros than cons for women, and is one of the main reasons that women live around five years longer then men on average.

Many hair loss forum members (and body builders too) take an aromatase-inhibiting prescription drug called Arimidex that prevents estrogen levels from rising when on Finasteride.  I would never add yet another drug to my life considering how much I hate taking just one at the moment, but Arimidex seems to be a fairly popular and safe drug as far as I can tell.

Estrogen 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 any interest upon first glance.  For one, estrogen is a female hormone, so what male in his right mind would want to start taking estrogen and getting female secondary sexual characteristics and increased fat deposits  among other side effects?! Estrogen does have some beneficial properties for the heart, and is though to be one of the main reasons behind why females outlive males. However, I would still pass on it.

The reason I decided to write a post on estrogen, however, is because I recently read an extremely interesting 4 page interview from 2012 of our omniscient hair loss hero Dr. George Cotsarelis. While the main part of the interview is devoted to the oft discussed PGD2, there are a few other interesting subjects discussed.  The second page of the interview is what really surprised me in a good way.

On page 1 of this interview, Dr. Cotsarelis discusses the old and well known Dr. James Hamilton study from the 1950s in which it was found that men who were castrated before puberty (eunuchs) never went bald, but upon being given testosterone, those with a family history of baldness still started to loose hair.

On page 2, however, Dr. Cotsarelis mentions something that I had never read before and that got me quite excited: basically, even after someone has lost much of their hair due to androgenic alopecia, they can regrow a lot of it when given estrogen after castration!  His point is supposedly verified by many studies on transgender (I assume male-to-female, aka MTF) patients showing hair regrowth after their being castrated and getting on estrogen therapy.  While I do not think any of us men want to get castrated or take estrogen, this is still an incredible finding.

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/becomes extremely fine), it can never return.  This is also why Finasteride and Minoxidil virtually never get back any significant amount of hair for someone who is mostly or entirely bald.  There have been anecdotal posts on internet forums about Dutasteride actually regrowing large quantities of vellus/invisible-to-the-eye 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 long lost hair when on Dutasteride, but that whole episode was controversial and not replicated.

More  recent research has suggested 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.  In this 2012 interview, towards the end Dr. Cotsarelis mentions that perhaps blocking PGD2 will allow the stem cells to make progenitor cells again.   However, this is not a certainty, and neither is there a given that long lost hairs will regrow again 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, since many/most older balding MTF transsexuals seem to get hair transplants even after getting castrated and getting on estrogen therapy.  I was planning to write a couple of posts on MTF transsexuals this year, and hopefully I can get more direct feedback from some of them on this highly interesting issue.

Another important thing that Dr. Cotsarelis mentions on page 2 is that there could be an inflammatory component to hair loss.  This also surprised me, because he seemed to be saying the opposite just two years later when being interviewed in 2014 (in response to Dr. Brett King’s groundbreaking results in curing alopecia areata) when he said that androgenic hair loss probably does not have an immune system component to it like alopecia areata.  Am I misunderstanding something here in the contradiction?  Doesn’t an immune system attack imply inflammation?

Finally, for men who take Finasteride (brand names Propecia, Proscar, Finpecia, Fincar etc…), one potential side effect is increased estrogen levels, which sometimes results in the dreaded gynecomastia along with fat gain in other body areas.   Their are numerous complaints on hair loss forums about this.  So besides the fact that estrogen therapy is not of much use unless you get castrated, another reason for a man not to take estrogen in the hopes of growing back some hair is…. man-boobs.