How Does Finasteride Impact Testosterone and Estrogen?

Ever since I first started taking Finasteride a decade ago, 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 Finasteride once every two days instead of 1 mg every day. I stuck to generics and did not take the more expensive brand name Propecia.

Some people prefer natural DHT blockers. Although these are far less effective than Finasteride, they are usually side effect free. Note that I am aware that there are numerous people who take 5 mg of Finasteride (Proscar) per day for enlarged prostates. They generally seem to get limited to no side effects based on various studies, so perhaps I am overly cautious.

Edit: I now take the much stronger Dutasteride to treat my hair loss.

Finasteride Chemical Structure
Finasteride Chemical Structure.

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 (aka the female hormone) levels. This tends to be the number one concern of people taking the drug when it comes to side effects. Higher levels of estrogen (oestrogen) in men can result in feminizing effects.

These include gynecomastia (enlarged breasts in men), increased body fat levels and sexual problems. Note that estrogen can also lead to hair growth. That is why male to female transgender persons take estrogen injections or patches.

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 my answer in an official brochure from the manufacturer of Propecia, Merck.

In there, it states the following: “mean circulating levels of testosterone and estradiol were increased by approximately 15%“. Estradiol is essentially the same as Estrogen (see next paragraph). However, now I needed to find out how estrogen levels in men that go up by 15% compare to levels in women.

Types of Estrogen

There are three types of naturally occurring estrogens in women:

  • Estrone (E1).
  • Estradiol (E2).
  • 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. 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.

Update: A 2019 study from the US concluded that 5α-Reductase Inhibitor therapy is not associated with consistent and significant increases in serum testosterone levels.

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 the culprit. 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. The subsequent change in this T/E 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. However,  higher estrogen levels in women also mean substantially higher rates of breast cancer in comparison to men. Ultimately, the pros outweigh the cons. Low testosterone and high estrogen are among the main reasons that women outlive men by around five years on average.

Many hair loss forum members (and body builders) take an aromatase-inhibiting prescription drug called Arimidex. It supposedly 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. Arimidex does seem to be a fairly popular and safe drug as far as I can tell. It is still best to consult your doctor or dermatologist first before taking such drugs.

Finally, make sure to read my post on dutasteride (Avodart) and finasteride (Propecia) dosage discussion. Some of the reader comments in there are very useful.

37 thoughts on “How Does Finasteride Impact Testosterone and Estrogen?”

  1. There u go u, as you can see no problems!! Stop being afraid and take finasteride, has been keeping my hair since 18 and I’m 25, never had side effects.

  2. I’ve got mild Gyno after 1 week on 1.25 fin ED.

    I was taking fin for 2 month and stopped 10 days ago.
    When my hormones will stabilize? Will my gyno go away? It’s not noticeable but I feel it under my nipples.

  3. Great post thanks man…. Once you get past the scaremongering about fin and look at the stats out there , it does seem like its worth a shot if you know just how badly losing your hair will affect your self esteem. I haven’t started on it yet but it really think I will give it a try. Think i’ll get my blood work done first just to be safe and see how my hormones change later on! Also going to start on 0.5 mg to see how body treats it! Keep up the work dude all posts appreciated

    1. Thanks. The only other big issue is whether reducing DHT by so much has any harmful effects in the long run. A recent 10-year study did not find any long-term problems and I look forward to more such long-terms findings being published in the next several years. Finasteride was approved for treating BPH in 1992 and for treating hair loss in 1997, so we might get 15-20 year studies pretty soon.

    2. Hi did you ever get your blood work before and after? Did you try finasteride? How did it go for you?

  4. ADMIN this is a study report saying that finasteride does not cause undesirable sexual side effects.
    J Androl. 2008 Sep-Oct;29(5):514-23. doi: 10.2164/jandrol.108.005025. Epub 2008 Apr 17.
    The effect of 5 alpha-reductase inhibitors on erectile function.
    Canguven O1, Burnett AL.
    Author information
    The 5 alpha-reductase inhibitors, which inhibit conversion of testosterone to dihydrotestosterone, are used for miscellaneous clinical applications, including the treatment of benign prostatic hyperplasia and male pattern hair loss, and for possible reduction of the risk of prostate cancer. Erectile dysfunction has been associated with 5 alpha-reductase inhibitors. Overall, reports in the literature suggest rates of erectile dysfunction to be between 0.8%-33% in men using these medications. However, randomized controlled studies report the rates of erectile dysfunction to be between 0.8%-15.8%. The possible risk association is that these medications impact androgen function, which is understood to contribute to normal erectile physiology. The 5 alpha-reductase inhibitors result in a drop in median serum dihydrotestosterone levels by 60%-93% within 2 years, but there is no major change in testosterone levels. In this review, we surveyed studies on erectile dysfunction in patients treated with 5 alpha-reductase inhibitors and critically examined the evidence that associates 5 alpha-reductase inhibitors and erectile dysfunction. We conclude that 5 alpha-reductase inhibitors do not lead to erectile dysfunction to a significant degree, and we support the position that dihydrotestosterone is less relevant than testosterone in erectile function.

  5. There’s a much bigger problem about finasteride than any of the above: try Googling for articles on finasteride and Alzheimer’s.

  6. Also, finasteride works by blocking the conversion of testosterone to dihydrotrstosterone — but unfortunately it also interferes with the natural conversion of progesterone (via dihydroprogesterone) to alopregnanolone. (The alpha-II redustase enzyme which finasteride suppresses is essential to both of those conversions). Allopregnanolone is an important neurotransmitter necessary for proper maintenance of the myelin sheaths which protect neurons in the brain and spine, and a deficiency of it can therefore result in neurological diseases of “demyelination” — e.g. Parkinson’s disease and multiple sclerosis.

    Increasing your risk of Parkinson’s, multiple sclerosis and perhaps even Alzheimer’s disease in order to preserve a youthful-looking head of hair is not a cool idea. You mess around with your body’s natural hormonal and neurological system at your extreme peril.

    1. The increased progesterone from finasteride can also cause skin discoloration known as melasma.

      The peer pressure just do it guys are irresponsible.

  7. I agree with Michael. Too many folks these days are not intelligently cultivating what they allow in the soil of their minds. Reports on studies conducted by organizations that have something to gain, will always benefit the drug maker.

    I was on Propecia for 10 years, and only thought that everything was normal, because I was so far removed from what it really felt like to be normal. I developed Hashimoto’s Thyroiditis and Low T while on this drug, not to mention genital shrinkage.

    It was only until I gave up reading the online endorsing articles in favor of finasteride usage on the net, I decided to stop the drug and see an Endocrinologist. My T levels dropped below that of some women. Serum levels are negatively impacted over the long haul. Don’t buy into the hype, or what other people claim. It may not affect some as bad as others, but why play Russian Roulette with your God given hormones, like DHT, which is what makes us men. I gambled and lost.

    Furthermore, you may want to check out the latest studies on BPH. Some studies suggest that DHT is not directly linked to BPH, but rather the imbalance in estrogen and testosterone.

    1. More importantly, is there a way of monitoring these potential effects earlier on in the process of taking fin.
      Blood tests etc…?

  8. I bit the bullet and just shaved my head. It takes some getting used to but I decided to do this rather than continuing to take finasteride. I took finasteride for many years (off and on). I’ve been off of it for about 3 years now. I would exercise some caution using any kind of medication. This medication never affected my ability to have an erection but about 3 yrs ago when we tried to get pregnant, it didn’t happen. I’m not certain if it was a possible side affect of using finasteride for so long or whether my partner had issues. I suspect the latter because she had never had kids before and was up in age. Nevertheless, I’d be careful using it. I’m glad I’ve been off of it for some time now.

  9. What about topical finasteride solution with minoxidil applied topically to scalp. Seems a lower level would enter the blood stream. Would it not be just as effective applying it locally (scalp)

  10. Been taking fin for years (1.25 mg per day – split 5mg generic into quarters). Takes about 6-9 months to notice difference in hair growth. Combine with rogaine at first. Once the fin kicks in, u can stop the rogaine. No notoceable side effects. I think they are listed more for people taking the 5mg for prostate enlargement. Overall, worth it to prevent baldness. Important to start BEFORE u lose too much hair.

  11. Just started Fin two days ago, geez what andelressig thread. My thought on some posts,
    1. If a low dht level contributes to alz and parkinsons, wouldnt you see a correlation between older men with hair and those suffering from those diseases? Think fin would be only one of many variables to that equation.
    2. My body fat is relatively low alreay and I feel as if my Test level is also low, I’ve drank green tea daily for years and def think there’s truth to it affecting Test levels, and DHT as a result. When I’ve had weeks of not drinking it, I could feel the pump, energy, growth, of working out a lot more than when I do drink it.
    3. 34 and pretty full head of hair except for one temple side, which is why I’ve started Fin. Since fat cells more readily convert the test to the female estrodil, I’d be interested to see the age/body fat/and normal Test levels for anyone who developed “man tits”, I’d be willing to bet that correlation of the 2-3% reporting side effects is pretty hi

  12. A person in my family took finasteride and it totally ruined his life. Severe adverse effects to his brain and the body – and he only took a few doses.

    Perhaps the risk is small (and perhaps it’s higher than the drug manufacturer would want you to know), but if you’re unlucky enough to be in that “small” adversely affected group, you will be very sorry you ever heard of finasteride.

  13. I’ve taken Finasteride, 1.25 mg each night, for 2 years now. I have monitored it very closely and have experienced spontaneous ball ache and watery semen. I have a good head of hair still, although I do not believe I have additional growth. My father in law is 25 years older than me and experienced ED after 1 week of taking it. He stopped and the side effects were gone a week later. Just one experience, but for what it is worth that has been my experience

  14. any idea about women taking 5mg of finest? cause this has been prescribed to me a 40 year old woman with thinning. Im very skinny with mild hirsutism and acne/oily skin.

  15. I’m 27 & have been on Fin. 1 mg/day for ten days….almost from 2nd/3rd day onwards have experienced a flat 40-50% reduction in ejaculation volume! & a less stiffer erections

    PS: a week before taking the fin I also began using ‘natural herbs’ which claim to enhance libido & other similar stuff & to my surprise, its effects were positively conspicuous from the 2nd-3rd day itself but once i started the fin, it seems ‘taming’ it outright (60-70% nullification)
    Also, I would like to add that in around the same period I have been in ~ 500-600 calorie deficit/day (vis-a-vis 2000 cal./day requirement) as I want to attain a healthy BMI

  16. I’m 61 and have been taking 1.25 milligrams of finasteride for a couple of years now open reading a lot of the thread about testicle aches and whatnot but because of my prostate pph I would get some pain down there particularly if I had a stressful day but oddly enough when I went on the finasteride it went away and only came back when I ran out and forgot to buy it for a week or so then the pain would come back after about 1 week then completely disappear again when beginning the finasteride treatment so this flies in the face of what I’ve been reading on this thread.

    My hair is definitely much improved over this period of time also I workout every second day very intensely for about 10 minutes only I get my heart rate write up push ups chin ups squats dumbbell presses and I really believe I’ve never been in better shape you can almost see my abs now which I’ve never had in lot life before my friend’s agree so this lowering of the dehydrator testosterone which allows free testosterone to be raised must have something to do with it also oddly enough my body hair has decreased very noticeably in this time I used to get my daughter to shave my back every summer but now there’s barely anything they’re not even worth thinking about doing so it’s been all a very good experience for me and have no desire to stop anytime soon.

  17. I’ve been taking about 1 mg finasteride for about 15 years with no I’ll effects. Feel great, 65 years old, a little bit decrease in semen production overall. But I can live with that, no acne, no psychological side effects feel great. I buy finasteride for prostate and cut them into 1.25 mg pills with a pill cutter. It’s a lot cheaper than buying Propecia plus it keeps your prostate from enlarging, which happens to almost all men if you get old enough. Never had any prostate problems. Dan

  18. It appears that the 15% increase in mean circulating levels of testosterone and estradiol were caused by 1 mg of Finasteride per day. What about the 5mg per day dose? How much will it increase those levels?

  19. Fin saved my hair and crushed my libido never to return. Semen volume miniscule compared to pre-fin. Flattens emotions. A parade of nude women wouldn’t get me aroused these days.

    I’m 40’s, married with almost grown kids so I can survive without a raging sex desire but for your younger men, women care more about the length of your erection much more than the length of your hair. Don’t take it. No problems with Rogaine and it works so go with that.

  20. Male, 57
    Been taking 1mg Fina (AKA Propecia) since it 1st came on the market for hair loss. No adverse affects. I am (back to) body building. @ 50 was diagnosed with stage IV Colorectal cancer. Had to stop all my meds…. for the chemo. Now, back 7 years cancer free. I was using 600mg test a week prior to all this. No gyno.. no nothing just strong as hell and big gains. I guess it depends on your DNA. Some people smoke an entire life time and nothing… and some people smoke and poof… lung cancer. All I am saying is monitor yourself, do the research and make a decision. You WILL know if it is for you or not. BTW… full head of hair and MPB runs in my fam.

    1. Congratulations on overcoming cancer and keeping your hair SCD!

      So you were taking 600mg testosterone from what age to what age? And why did you stop?

  21. I am a Female who had stage 3 breast cancer 11 years ago. I have Alopecia now due to Lupus. I suppose to not have any hormones or estrogen. Does Finasteride have this if women take this drug? Thank you.

  22. 22 born male, gender fluid here. I’ve been on finasteride for a lil over a month and my libido has gone up by a lot. I usually mas****te at least twice a day but now i’m up to 4-6 times, even ejaculate more and further, and stay erect for longer. My doctor recommended Nutrafol (supplement) first, and it too skyrocketed my libido. Same thing with fin it seems…

    My hair loss started when i went through a depressive episode at 17 and just got worse with the years, even lost half my beard, lashes and eyebrows. My lashes have already grown fuller and longer. Guess it’s all genetics

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