Category Archives: Testosterone

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.

Are Obese Men Less Likely to go Bald?

I think that obese men are slightly less likely to be bald than people of lower or normal weight. My guess for this is due to the favorable scalp hair growth effects of extra estrogen and lower testosterone in obese individuals.

When I wrote this post, I ran a poll and only 26 percent of people agreed with my hypothesis. Another 31 percent were unsure. The second half of this post is from 2017 and has those details. The first half is an update with new findings that contradict my hypothesis.

Obesity and Increased Hair Loss

Earlier today, Dr. David Sinclair posted a link to an interesting new Japanese study titled: “Obesity accelerates hair thinning by stem cell-centric converging mechanisms.” Apparently, obesity-induced stress targets hair follicle stem cells (HFSCs) to accelerate hair thinning. Excess body fat induces stem cell inflammatory signals which accelerate the miniaturization of mini-organs and repress regeneration. Obesity also leads to marked inhibition of Sonic hedgehog (SHH) signaling.

Moreover, a 2014 study from Taiwan concluded that a higher body mass index (BMI) was associated with a greater severity of androgenetic alopecia (AGA). However, in this particular case, the findings only pertained to those who already suffered from AGA. There was no proof that obesity could actually spur the onset of hair loss.

Do note that obesity due to excessive food intake likely has different hormonal effects in comparison to obesity due to excessive alcohol intake. And obesity due to existing thyroid or pituitary gland related  hormonal disorders is also very different.

Despite the above new Japanese study, I am still not convinced. The hormone altering modern diet and lifestyle is likely more of an issue in causing rising rates of balding around the world. Rather than  just actual weight gain. But my opinion and guessing does not mean much of course.

High Body Mass Index and Better Hair?

May 13, 2017

Last week, a new study from Germany concluded that short men are more likely to go bald prematurely (i.e., at an earlier age). This was very surprising to me, since I never noticed any strong correlation between height and scalp hair quantity in real life. The same study also alluded to the fact that “white men in particular lose their hair prematurely”. Something I have also observed and mentioned on this blog before. The above study was widely covered by the global media.

On the other hand, one correlation that I have definitely noticed is that men who are obese seem to on average have a at least modestly lesser chance of balding in comparison to: men who are of average weight; or are slightly overweight; or are slightly underweight. For the sake of simplicity, assume that the definition of an obese man (of average height) is someone who is at least 50 lbs overweight.

On hair loss forums, people often talk about changing their diet to a healthier one in order to see if it improves scalp hair. However, if anything, I have seen highly obese people with a terrible junk food and soda filled diet having better hair than those with more regular diets. I hope I am wrong about that observation.

Moreover, when people lose a lot of weight, one frequent complaint seems to be the side effect of hair loss. This might be a temporary shedding (telogen effluvium) problem in most cases.

Obesity’s Impact on Testosterone and Estrogen

If the above inverse correlation between weight and scalp hair quantity is true, the main reason is probably because very fat men tend to have lower levels of testosterone. This would mean they most likely also have lower levels of dihydrotesterone (DHT), the main culprit in male pattern hair loss. An important study from 2008 found that higher waist circumferences were associated with lower testosterone levels.

It seems like obese men might also have higher estrogen levels, which can benefit scalp hair significantly. See my post on estrogen and hair growth.

Update: I had to delete the poll in 2018 due to some plugin issues. The results of the poll are summarized below.

In your daily life, have you noticed that obese men are less likely to go bald in comparison to non-obese men?

Total responses = 1,380.

Yes = 362 (26.2%).

No = 595 (43.1%).

Not Sure = 423 (30.7%).

Obesity and Hair Loss.
Obesity and Hair Loss.