Syntheroid Testosterone Booster Review: Does It Work?

When I first heard the name Syntheroid I thought it was a supplement for the thyroid because its name sounds a LOT like the drug synthroid that people take for hypothyroidism.  But Syntheroid is billed as a natural testosterone booster whose motto is “power, mass, sexual performance.”  The makers of Syntheroid  claim that it can improve speed, agility and reaction time, as well as muscle size and strength.  This is in addition to the claim that Syntheroid can maintain libido during hard core dieting.  These are all pretty bold statements so I’m not surprised if people wonder if Syntheroid really works or not?  Let’s now review Syntheriod and what can be discovered. Also see my review of the HGH supplement, SeroVital.


Who Makes Syntheroid?

If you check the product website – -you can’t find out who makes this product.  Its only after some digging that I discover that syntheroid is made by a company called XPI (  Why the XPI website is not listed on the website does not make sense.

The address of XPI labs is 965 N 1430 W  Orem, UT 84097.  The link provided is to show what the area looks like.  I see a lot of warehouses.  I did not see any building called “XPI laboratories” but since most of the buildings appeared dull looking – built for function, rather than looks –  I’m sure its in there somewhere.  XPI labs does not seem to have a BBB listing when I checked on 12/7/11.

On the website there is a video of a 31 year old man named Josh Dahl (“The Josh Dahl Story”) where he says that Syntheroid makes him feel like he’s 21 years old again.  They listed his name like we should know who Josh Dahl was – which I didn’t – so I did some goggling on who Josh Dahl, was but could not find anything.  Maybe Syntheroid did do what Josh said but in general I take all testimonials from people I do not know with a big grain of salt.


Syntheroid Ingredients

Kudos to the Syntheroid website because they do tell us what’s in this product. If you take 3 capsules of Syntheroid -the recommended dose – you get the following:

Tribulus Terrestris 650 mg
Testofen 300 mg
Aminogen 250 mg
Coleus forskohlii 125 mg
Milk Thistle 120 mg
Alpha lipoic acid 100 mg
Eurycoma Longifolia 100 mg
Horny goat weed 100 mg
Bioperine 15 mg



Remember, even though the name syntheroid sounds like a drug, syntheroid is not a hormone or a pro hormone. It’s a dietary supplement. They even say this on the Syntheroid website.


Looking over this list of ingredients, Syntheroid has some things found in many other products I’ve reviewed in the past.

For example, Syntheroid has Tribulus. I know people have said that tribulus works for them but I have been skeptical about the claims of this herb since the 1990s when it first started getting popular. For more on this, do read my Tribulus review after your done reading.

Despite the hype about tribulus and testosterone, I can’t find any proof that it works. For example, in a study published in 2001, tribulus didn’t work. In another study from 2007 tribulus didn’t work.

If anybody knows of a“tribulus raises testosterone study”, please let me know and I will happily update my reviews on this herb.

Now, no study is perfect, so if you really want to know if tribulus raises testosterone, get your doctor to check your testosterone before starting tribulus (or Syntheroid) and after a month of using it.  This is the only way you can know for sure if it worked or not.

As for Testofen, it’s a cool sounding name and was likely invented to give the impression that it raises testosterone – but it doesn’t. Testofen is just an made-up name for the herb Fenugreek. For more on fenugreek- testosterone research also see my review of Ageless Male.

Fenugreek might raise insulin levels. Since insulin helps us use amino acids, that means it has a mild anabolic effect. I’m guessing this is why it’s in a testosterone booster supplement. Here is Fenugreek on Amazon.

Ironically, this effect on insulin is why fenugreek is also found in diabetes supplements.  For example, the diabetes supplement Glucotor V2 also has fenugreek. In fact, this diabetes supplement has the same amount of fenugreek – 300 mg – as Syntheroid does.



The Syntheroid website says that Aminogen is a ” proprietary proteolytic synthetic enzyme” that  “was created to improve protein digestion and absorption.”  That means at that Aminogen is not an amino acid supplement but rather just a fancy name for a protein digesting enzyme supplement.

Unless you have a problem absorbing protein you don’t need enzyme supplements.  They say that Aminogen “works to produce a higher bioavailability within your body particularly to your muscles.”  So, where is the proof of this?  As far as I can tell neither Aminogen – or Syntheoid – has any peer reviewed clinical proof that it does anything.  Since they can’t prove to me that this statement is true, I discount it.


Just a heads-up, animal protein – has a very high absorbability, so unless your doctor has told you that you have a problem with digestion, you don’t need any supplemental digestive enzymes.  What’s a good way to remember animal protein? It’s any food that had a mother. That’s how I remember it!


Coleus forskohlii

This herb is said to be a metabolism booster and weight loss supplement. The idea here is that coleus forskohlii (forskolin) stimulates fat burning enzymes that help us lose weight. One small study of older, overweight men also noted that coleus forskohlii increased testosterone levels.

This is the logic why Coleus forskohlii is found in many weight loss products such as Lean and Fab and Apidexin to name a few.

Here is coleus forskohlii on Amazon.

The problem with coleus forskohlii research is that they often have problems and so for the moment, I will keep an open mind about forskolin until better research is done. For more on this research, read my Coleus forskohlii review.


Milk Thistle

Since steroid abuse is thought to damage the liver, and since Syntheriod is reputed to be a testosterone booster, I’m guessing this is why they added the liver protecting supplement -milk thistle – to Syntheriod.

That is the most obvious answer I can guess, because there seems to be no clinical proof that milk thistle raises testosterone or improves libido. There is interest in milk thistle for diabetes because it has been shown to reduce blood sugar levels.

Might stabilizing blood sugar levels help people have better workouts? In theory, maybe. This might be another reason for putting milk thistle in Syntheroid.

Mostly this herb is an antioxidant and one of its active ingredients is a compound called Silymarin.  Syntheroid has 120 mg of milk thistle but I can’t tell from the product website how much Silymarin this translates into.


Alpha lipoic acid

Like milk thistle, alpha lipoic acid has also been researched for its blood sugar lowering effects.   I’ve seen this stuff used in many exercise and weight loss supplements despite any good proof it helps weight loss or exercise.

For example, alpha lipoic acid is also found in the bodybuilding supplement Stemulite and Jillian Michaels Fat Burner as well as the Plexus Slim weight loss supplement.

Like several other ingredients in Syntheroid, eurycoma longifolia is found in variety of other products. For example, this herb is one of the main ingredients in TriVerex – a male enhancement product you may have see on late night TV.

It’s probably eurycoma longfolia – as well as horny goat weed – that are at the heart of the claims that Syntheroid improves sex. I don’t want to reinvent the wheel on these ingredients, so please read my words on TriVerex” for more info on the research behind both eurycoma longfolia and horny goat weed.

The same thing goes for Bioperine. For more on this ingredient see my Lean and Fab review.


Syntheroid Side Effects

I think if you are healthy you might not notice any side effects with Syntheroid.  If you are not “healthy” or take any medications, see your doctor first.  Syntheroid is probably very safe in healthy people but as far as I can tell this assumption has never been tested. Here is Synteroid on Amazon for those who want to check out the comments from others who have used it.

One older study noted that alpha lipoic acid might lower thyroid hormone levels.  If this holds true, it might also reduce vitamin D levels as well as metabolic rate.  I’m not sure if this “side effect” is true or not  but it’s worth mentioning just in case you have hypothyroidism. Alpha lipoic acid might also add to the effects of insulin and other diabetes drugs.

Fenugreek might cause hypoglycemia (low blood sugar) and interact with insulin or other blood sugar lowering medications.  It might have an even greater blood sugar lowering effect when combined with alpha lipoic acid.

Milk thistle might interact with many medications like coumadin (a blood thinner). The herb might also have an estrogen effect that might be bad for women with a history of breast cancer. This effect is probably a long shot, but speak to your doctor if you are not “healthy” just to be safe.


How much does Syntheroid cost?

They say 1 bottle currently costs $59.95 on the Syntheroid website. I think that is a lot of money for a product that has zero clinical proof that it works.

Here is Synteroid on Amazon to compare prices.


Does Syntheroid Work?

Well, on the XPI labs website they say that Syntheroid “was scientifically formulated to boost testosterone levels, improve protein synthesis, absorb nutrients, and burn fat faster than any other legal supplement on the market.”  Scientifically formulated?  How did they scientifically formulate this product but did not conduct any scientific tests to prove Syntheroid actually does what they say?

In my book, you can’t invoke the name of the mighty god science (lowercase g) without following through by doing actual scientific testing – in humans.  Failure to do so is just bad science.  They also say that with Syntheroid, you can boost testosterone by up to 400%.  Again, where is the proof?  Actually if you look closely at the XPI labs website, they didn’t really say Syntheriod would boost testosterone by 400%.  Rather, they just plastered the saying “Boost Testosterone by up to 400%” on the web page to make you think that is what it would do.  There is no supporting evidence for this claim.

I think Syntheroid is just another overpriced bodybuilding supplement that is long on marketing and short on science but I’m open to hearing what the users of Syntheroid are experiencing. If you are interested here is Synteroid on Amazon.

What do you think?


  1. Chad says

    I hate to sound harsh, but you could have skipped the “fluff” and gone strait to the ingredients.

    I don’t care if there isn’t a link to XPI supplements home page, they have a giant XPI logo on the bottle and the website.They obviously aren’t hiding anything,

    I also don’t care if their building doesn’t have an XPI logo on it. I checked and USPLabs, Cellucor, MusclePharm, BSM, and other big companies. They don’t even give you their address. Who cares?

    i love reading your reviews, but lets stick to the stuff that matters.

    • Joe says

      Chad, thanks for the feedback. I cover the stuff on the companies because I feel it adds to the totality of the review. Companies that have “lab” in the name gives the impression to me that they physically exist as a “lab” or do laboratory research and so pointing out that that this might not be so, I feel, adds to the review. I do try to make the sections easy to skim so people can get to the areas they are interested in quickly, so I hope this makes up for things.

    • walker mccutchen says

      I’m a man of 73 years, was on testosterone injections through my doctor for 3 years. they worked very well then stopped working. so I found a supplement (tongcat ally) it worked good for a couple years then it quit working. found syntheroid —had my testosterone checked at the va—it was 350—started taking the supplement and could tell the difference in about 10 days—took it about 3 months,went back and had my testosterone checked again and it was in the 500 range. its worked for me for a couple years now BUT I don’t take it every day—I take it say–10 days and quite for 5 days. I’ve found that many supplements work best that way.

  2. Greg says

    Joe, through all your research, if you were going to take a testosterone booster what would you recommend (take yourself)?

    • Joe says

      Greg, for me, none stand out because none of those Ive seen have given me any proof they would really work in people. Best I can say is get T measured before you try anything (free T and bound T) try a product for a month and retest T. Thats the only way to know for sure. Its good for all men to get their testosterone measured anyway at least to see if they are low or not and to get some baseline #s that doctors in the future might be able use to tailor treatments better.

  3. Roger Smith says

    Joe, is right, I’ve been on this product for the past 6 weeks, I have followed all the instructions, and done all the exercise, and saw no results, I feel the same way after taking this product, the only good thing about it is that they got a 30 days money back, and I returned my leftover. Thanks, Roger

    • Joe says

      Thanks Roger and for what its worth, sorry it didn’t help you but I am glad you were able to get your money back from the company.

    • Michael Castle says

      He said he used the product for 6 weeks, and it did not work and return what was left for his money back…..
      A bottle of Syntheroid contain 60 pills. Direction is 3 pills TWICE A DAY in other words 6 pills a day. A bottle therefore should last 10 days ….and this guy had leftover after 6 weeks??????

      • Treebunny says

        Lol…I took enough of that crap to make a billygoat puke but all it did was turn my p yellow. It’s easy to figure out. Anything you take by mouth has to go through the liver and kidneys and that amounts to nothing in the body. Pills are joke joke joke…

    • Joe says

      Dude, there was no D Aspartic Acid in Syntheroid when I reviewed it. Thanks for the heads up I’ll look at updating what I wrote.

  4. Powbeech says

    Reply to my own reply:

    it is possible that they improved the formula by adding this and other ingredients since your review.

    • Joe says

      Powebeech, supplement companies do update their formulas from time to time. Since I dont know when this happens, I do appreciate it when people like you tell me about this. D aspartic acid has been something Ive wanted to look at anyway so Ill update my review with this ingredient in the near future.

  5. Jimmy says

    Joe, what is your opinion on Gaspari supplements? I remember when I was younger Rich Gaspari was quite a beast in the gym world and I am wondering if his supplements are considered worth it.

    • Joe says

      Jimmy, Ive never heard anything bad about Gaspari supplements but my question is are they any better than other supplements that have the same ingredients?

  6. Bryan says

    Joe, I have been using Syntheroid for the past month. I started out having the sensation that it is working then about mid month the feeling declined. May be mental because, I was expecting so much. I was wondering about stacking it with Winni V. What do you think?

    • Joe says

      Bryan, if I understand what winni V is, its a steroid also known as winstrol (Cyclostanozol). You didn’t tell me anything about you so I could not even make an educated guess but to be honest, steroids, because they are not supplements, are outside my area of expertise but my general opinion is I would not use steroids to increase muscle mass esp if you are young.

      • Bryan says

        Thank you for your advice. I am 41 years old, I’m in the gym everyday. They advertise Winstrol as a top legal steroid, I trying to read up on what makes a steroid legal and nonlegal and is it possible. I will stick with the supplements..Thanks again.

  7. Steven says

    Joe, Is there any supplement that is making claims towards improving muscle mass and libido that you support because they back their claims with peer reviewed published research?

    • Joe says

      Steven, so far I have not found one. I do keep my eyes open but so far I have not found anything that I had faith in.
      I think the best thing for all men to do is to get their testosterone levels checked (preferably in the morning) and to get a baseline of what it is. this will help future doctors have an idea of what it was when we were your normal, in case there is a time when we might need testosterone therapy.

  8. Charles says

    I’m not trying to alarm anyone more of a fyi. I took Syntheroid for 3 months with positive results. It elevated my testosterone level to above 670. Recently I was diagnosed with stage II prostate cancer. Prior to taken Syntheroid my PSA level was normal. In 1 year I’m facing surgery.

    Get the facts with elevating testosterone level with supplements and prostate cancer. Like I said before. I’m not yelling the sky is falling. Just read up on it. Especially if you are over 40.

    • Joe says

      Charles, so very sorry to learn of your prostate cancer. I’m glad this was discovered so you can get the surgery you need. We will likely never know if there was a connection to syntheroid or not. I will say a prayer for you that all goes well. I do agree that men should research what they put in their bodies and get regular prostate check ups.

      • Charles says

        Thanks Joe. I don’t mean that my taking Syntheroid has a connection to prostate cancer. Any supplement that increases testosterone can have an effect on the prostate. I took Syntheroid and had great results. No side affects and in 8 months I lost close to 60 pounds. Along with a more nutritious diet and exercise.

        • Joe says

          Charles, oh ok. well I’m just glad you had this caught in time. I looked up stage 2 after you left your comment and it looks like you caught this in time, something I’m really happy for. I’ve known several people who are healthy and cancer free after having the surgery.

  9. MikeD says

    Honestly, If one reviewer has proof it increased T and that it created a prostate problem, its not something you can ignore or dodge by apologizing for his situation, showing sympathy does not work on males (intended audience of your reviews here), it only makes us think you have too much estrogen in your body.

    I am a computer guy, 45 years old researching to find a solution like many others reading this. Im not an expert nor do I have any affiliation with any supplement or pharmacy type company. So the following comes from a typical guy with little or no expertise on diet and supplements.

    Sure you can hang on the “science didn’t prove he got cancer by increased T” but thats just a way to hide in the stream and hype of reviewing something and in a way that makes us think you have an opinion that seems credible based on XYZ facts.

    Well I take issue with that because you seem to have a good understanding of a lot of these chemicals, or have done just enough research to be able to talk about them like you understand them, however the real thing we are all looking for is an honest unbiased approach.

    Unfortunately your tactics cause me to feel you are very biased in that you crave for people to read your reviews instead of actually providing valuable information. For example, you use the word supplements frequently as if its a specialty of yours. I have yet to see you say anything about DHEA in any of these comments stating “I do not know of any supplement that can help increase T”. With DHEA being one of the most common supplements in the world with thousands of scientific results proving it for male and female hormone boost I must conclude that you are only creating a one sided review just to get the viewers and building on the existing hype.

    If I read your review of Syntheroid and you ended it by saying, based on scientific evidence you will likely get additional T, free and otherwise by taking DHEA. That would be an “honest” approach that I would actually believe and give you respect for.

    Summary: Being a claimed supplement guy how could you not know about DHEA, and in addition telling people you know of no supplement that can scientifically increase T. Those two things combined in my book discredits your review of this product and similar products, I might even go so far as to say I cannot trust any reviews you have ever created just because of this conclusion.

    • Joe says

      Mike D, DHEA was not part of this discussion and that’s why I did not mention it although I do have a chapter on DHEA in my book and I’m sure I’ll eventually get to covering it here as well. That said, why dont you get your free and bound testosterone, total testosterone and estrogen levels checked and then try DHEA for a month and get another blood test. Email me know if there is a significant change.

      • MikeD says

        I never said it was part of the discussion, however it should be if you can leave comments like this in multiple places in the comments section:

        “Joe says
        September 24, 2013 at 3:44 pm

        Greg, for me, none stand out because none” (Supplements) ” of those Ive seen have given me any proof they would really work in people.”

        I have not read your book. I am guessing you have done a lot of research on it, and I suspect you reference one of the thousands of scientific studies providing proof that DHEA supplements help the male body create Free and Bound T, and only a few studies say it increased T zero %. Then you comments above and tell others there is no supplement that gives you proof it really works in people.

        Maybe you have an explanation why you said that several times in the above comments section, or maybe you don’t think DHEA lab tests are real.

        Having taken DHEA from various manufactures attempting to solve my low T levels following the advice from my Dr who ordered tests in between those stages I can tell you that Free and Bound T increased for me, but little performance gains in the bedroom and muscle mass.

        DHEA being the building blocks for your body to create hormone means it wont happen unless it needs it, estrogen is needed in part of the male body just like T is needed in the female body, if it gets created, its needed for something.

        If you are lacking T or estrogen, and then force it in your body, you might create a problem such as the guy above pointed out with his recent diagnosis of cancer. I am hoping to raise T above what my body thinks it should be so that I can get improved performance, but safety concerns has me researching all this stuff, especially comments like the one from Charles and you glazing over it along with your statement on zero Supplements help boost T caused me concern.

        I do not normally create comments or blog and I am not trying to harass you but wish to determine what I can and cannot trust by pointing at what seems in conflict with the most scientifically analyzed supplement in the world called DHEA, one of the only supplements that survived the BAN on drugs by the FDA. If you take too much, it does nothing (consider it water soluble), if you don’t take enough you may not have enough tools to create T and forced injection of T will likely cause cancer because in that state its a free radical.

        However if your body creates it normally or another harmless chemical signals the body to create T then you are less likely to see free radical results because the proper chemistry for your specific system was used and the intended creation has an immediate destination.

        Combine DHEA with some of the things included in this (Syntheroid) product above and you might actually get results, I have no idea. To me it’s like saying, not drinking enough water will prevent you from building muscles, and that is the case no matter what you supplement because your body wont have the basic building block of all human organic chemistry.

        You cant list all the requirements in a review of a T booster product, (sleep, exercise, hydration, etc), but I believe DHEA is far more important than water or sleep, and it something found in other T booster designed products that no one is talking about it, it might be why this product isn’t producing as much results in Every customer they have. I want to know why…. I am extremely frustrated at having to become an expert in order to get results, and I would prefer to lean on reviews like yours. Does that make sense?

        • Joe says

          Mike D, have you tried DHEA? Did it raise your testosterone levels? I can say all sorts of stuff but in the end if it really is so well studied, then give it a try and see what happens. I’m really not trying to be smart – really! – but no matter what I say, I’m afraid it won’t satisfy you unless I tell you it works like most other websites probably do – and that’s not something I’m prepared to say. I’m not convinced because DHEA is complicated. If I remember correct, believe its 2 chemical steps from both testosterone and estrogen. That’s why I suggested getting estrogen tested as well. There is a lot we dont know about DHEA. Here is a nice review of DHEA which summaries a good amount of the research. you may have already seen this in your research.

          Regardless I do feel getting your testosterone level checked is a good idea. Are you sure you have “Low T”?

          • Charles says

            Hey Guys,
            Yes I’m the guy who just found out he has prostate cancer. Just a note here the Dr. gave me tons of information to read regarding this and different treatments.

            Comments on causes did mention as a possible I stress possible cause testosterone supplements.

            It also stated that years of fatty diets. Meats, fried foods fatty cheeses is also a contributor to prostate cancer.

            Recommendation is any guy 40 and over have the PSA blood test and start now to reduce your intake of fatty foods- the good tasting foods. Increase your intake of green veggies.

            Read up on prostate prevention. If you father had it between the age of 50 – 70 then you are a candidate for it through the genes your father left you.

            My dad didn’t have it. so I’ll say it was more my Italian food than anything else.

            Now regarding testosterone levels. My Dr will only do one test a year. I didn’t have one prior to taking Syntheroid but I did after I was on it for awhile. I do plan on going back on it after my surgery when I have the green light to return to my workouts.

            In no way am I associating my cancer to this supplement.. there is no medical proof. I’m 64 years old. I have lost 60 pounds and work out 4 times a week. My wife is 20 years younger than I am and we have a very active lifestyle.

            All I can say is this all happened while I was taking this supplement. I did get a nice shape not a massive bulk up. I don;t eat that much to bulk. My intent was to loose weight have the strength and stamina to complete my workouts and keep my wife smiling. I don’t plan on slowing down because of the cancer.

            To all the readers my word to you is take care of what you eat. Get PSA test when you hit 40. do your own research on this cancer.

            This is my testosterone test results that I had last year. I have not had another test since then. I will once I resume taking Syntheroid.

            Value Range
            Testosterone 603.39 300 – 890 ng/dL
            Please note change in reference range(s).

            Tanner Stage Male Female
            I < 30 ng/dL < 10 ng/dL
            II < 150 ng/dL < 30 ng/dL
            III 100-320 ng/dL < 35 ng/dL
            IV 200-970 ng/dL 15-40 ng/dL
            V 250-890 ng/dL 10-70 ng/dL

            Sex Hormone Binding 43 13 – 71 nmol/L

            Testosterone, Free 110.6 47.0 – 244.0 pg/mL

            The concentration of free testosterone is derived from a mathematical
            expression based on constants for the binding of testosterone to sex
            hormone-binding globulin and albumin.

            Testosterone, Free Pct 1.8 1.6 – 2.9 %

            I haven't heard of DHEA prior to reading it here. I would be interested in any results that can be provided. I will publish the results of my next testosterone test once I get it.

  10. Bryan says

    Hi Joe,

    Love this site. I have tried multiple test boosters from battle fuel xt (MP), maxgenics, Bioforge, Tropinol XP, and APE from AEN. I also take Indonesian tongkat ali from Pasak Bumi. I can’t say I noticed a significant difference as far as strength but my physique has made changes and I noticed the biggest raise in libido while on Tropinol XP stacked with Maca, and tongkat ali.

    I know I’ve laid out a lot of supplements, but I was wondering if you could comment on a few if you have time. Also no need to comment on the battle fuel, I had my testosterone tested before and after and it actually went down. Thanks and again thanks for your reviews!

    • Joe says

      Bryan, Ive never heard of most of the products you mentioned although if you know the ingredients in them, you can put them in the search box of my site. if I ever covered them, they will show up as parts of other reviews. For example, Ive covered both tongkat ali and maca several times. Really happy you are enjoying my website :)

    • Joe says

      Daryl, I know that D aspartic acid is popular in some T booster supplements. Right now I’m on the fence and would like to see more research. My spidey sense does make me think its more hype than truth though.

      For example, in this study, 3 grams didn’t raise testosterone or other hormones in people who worked out.

      On the other hand, in this study -on rats – it seemed to raised T levels:

      Is it possible it works in rats but not people? Maybe. I’m not sure yet. I’d like to see more people research.
      Hope that helps.

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