Testosterone Week: A Short Primer on How T Is Made

by Brett on January 15, 2013 · 41 comments

in Health & Sports, Wellness


In yesterday’s post we discussed the benefits of maintaining optimal testosterone levels and why you should care about your T. Today we’re going to look into the different kinds of testosterone that exist and how our body produces it. Grasping how testosterone works will help us understand why our own levels may be low and what we can do to boost it in our bodies.

Let’s get started.

The Three Sub-Types of Testosterone

Testosterone is a 19-carbon steroid hormone made from cholesterol that, as we discussed yesterday, provides a whole host of benefits. On average, a man’s body produces about 7 mg of testosterone a day, but not all of that T floating in our bloodstream can be used by our bodies. Our total testosterone can be broken down into the following three sub-types:

1. Free Testosterone. This is testosterone in its purest form. It’s the crack of testosterone, if you will. The reason it’s called “free” is because there aren’t any proteins attached to it. Unbound to other molecules, free T can enter cells and activate receptors in order to work its virile magic on your body and mind. Despite free testosterone’s benefits, it makes up only 2 to 3 percent of our total testosterone levels. To maximize the benefits of T, we want to do what we can to increase the amount of free testosterone in our bloodstream. On Thursday, I’ll share what science suggests we can do to help increase free T.

2. SHBG-bound Testosterone. About 40 to 50 percent of our total testosterone is bound to a protein called sex hormone-binding-globulin (SHBG). SHBG is produced in our livers and plays an important role in regulating the amount of free testosterone in our bodies. The downside to SHBG-bound T is that it’s biologically inactive, meaning our bodies can’t use this type of testosterone to help build muscles or boost our mood. SHBG isn’t bad, but too much of it is. Excess SHBG is why it’s possible to have high total testosterone levels, but still suffer symptoms of testosterone deficiency — the SHBG binds itself to too much testosterone and doesn’t leave enough of the pure stuff. Research suggests that diet and lifestyle changes can help reduce the amount of SHBG in our system, making more free T available.

3. Albumin-bound Testosterone. The rest of our testosterone is bound to a protein called albumin. Albumin is a protein produced in the liver, and its job is to stabilize extra-cellular fluid volumes. Like SHBG-bound testosterone, albumin-bound testosterone is biologically inactive. However, unlike SHBG-bound T, the bind between albumin and testosterone is weak and can be easily broken in order to create free testosterone when needed. Because albumin-bound testosterone is easily converted to free T, some labs lump it together with free testosterone whenever you get tested.

Where & How Testosterone Is Made

A small percentage of testosterone is made in the adrenal glands on top of our kidneys. But the lion’s share — 95% of it — is made in our testicles.

The process by which our testicles produce T resembles a Rube Goldberg contraption, except instead of mice and desk fans moving the process along, our body uses hormones. Below is the Reader’s Digest version of the complex process by which our testicles create testosterone.

1. The whole thing gets kicked off in our brain. When our hypothalamus detects that our body needs more testosterone, it secretes a hormone called gonadotropin-releasing hormone. The gonadotropin-releasing hormone makes its way over to the pituitary gland in the back of our brain.

2. When our pituitary gland detects the gonadotropin-releasing hormone, it starts producing two hormones: 1) follicle-stimulating hormone (FSH) and luteinzing hormone (LH). The FSH and LH hitch a ride down to our testicles on the freeway that is our bloodstream.

3. When the FSH and LH reach our testicles, they tell them to do two different things. FSH kicks off sperm production, while LH stimulates the Leydig cells in our testicles to create more testosterone.

4. Through a complex process that I’m not even going to attempt to describe, our testicles’ Leydig cells convert cholesterol into testosterone. That’s right, cholesterol is the building block of testosterone. Leydig cells get most of what they need to produce T by simply absorbing the cholesterol floating around in our blood from the bacon and eggs we ate in the morning. If there’s not enough cholesterol in our blood, our testicles can produce a bit of it so that the Leydig cells can convert it to testosterone. But relying too much on cholesterol produced by our nuts (of the non-almond variety) can actually inhibit our Leydig cells from producing T. You gotta eat those eggs!

5. Once T is produced, it’s sent back into our bloodstream. Most of it immediately attaches to SHBG and albumin, becoming biologically inert. The small percentage that remains free and unbound circulates around and starts manning up our minds and bodies. When our hypothalamus detects that we have enough T in our blood, it signals the pituitary gland to quit secreting LH so our testicles ramp down T production.

And that, my friends, is (roughly) how testosterone is made. Here’s a flowchart of the process for you visual learners out there:


Source: Wikipedia

As you can see, the process by which our bodies produce T is complex. This complexity means there are a myriad of ways it can get off kilter and cause our levels to drop. Just from reading about how T is made, you’ve probably thought of some factors on your own that might affect T levels. We’ll delve more into that on Thursday. All in good time.

Tomorrow we’ll take a look at what’s considered a “normal” testosterone level and explore the myriad of ways to get your testosterone tested.

Until next time, stay manly.

Testosterone Week Series:
The Declining Virility of Men and the Importance of T
The Benefits of Optimal Testosterone
A Short Primer on How T is Made
What’s a “Normal” Testosterone Level and How to Measure Your T
How I Doubled My Testosterone Levels Naturally and You Can Too

{ 41 comments… read them below or add one }

1 Dan January 15, 2013 at 9:07 pm

Thank you for addressing that men need cholesterol intake for proper hormone levels. IMO our exogenous cholesterol intake should be from sources that are limited in toxins, aka buy organic. Toxins are often stored in the fat. So when you eat food that had a bad diet, you get their toxins. As John Meadows says, “you are what you eat eats”

2 Ethan January 15, 2013 at 9:07 pm

Great Article!

The more I’m learning about basically everything; the more I see how balance seems to play a central role.

I’m looking forward to Thursday’s article.

3 RKMM January 15, 2013 at 9:14 pm

Exercise will trigger an increase in testosterone production to facilitate the formation and repair of muscles. The hormonal response will be correlated to intensity. To optimize the hormonal response to a workout you should interject small intervals of intensity every 20 minutes, just enough to keep the workout challenging without overworking.

4 Ryan U January 15, 2013 at 9:14 pm

Does the type of cholesterol (HDL/LDL) matter, or is one better than the other, in regards to producing testosterone?

5 Thomas January 15, 2013 at 9:16 pm

Looking forward for the next couple post

6 Miles January 15, 2013 at 9:16 pm

Great stuff, I can’t wait to see the rest of the week’s articles!

7 Joey Espinosa January 15, 2013 at 9:16 pm

You make this (former) chemist very happy.

8 Dr. John T. Alexander, II January 15, 2013 at 10:57 pm

When I saw that this article would discuss how testosterone is made, I thought there would be some discussion of bioidentical versus synthetic testosterone. Some doctors believe there is a significant difference in treatment effectiveness and safety between the two types. Hoping that maybe you will cover Low T treatment options a bit more in depth in your last installment.

9 Gavin January 15, 2013 at 11:36 pm

There’s an interesting study of older male runners on the type of workouts that will generate more testerone. http://runningmagazine.ca/2013/01/sections/news/study-speed-intervals-help-older-runners/

10 Matt January 15, 2013 at 11:49 pm

I wish it was Thursday already :)

11 Jordan Smith January 16, 2013 at 12:34 am

Not a lot of times on AoM where my biochem class comes in handy but I sure enjoyed this one!

12 Vincent January 16, 2013 at 3:17 am

Interesting read, thanks Brett.

I’ve read something of the same about organic food. I don’t know for sure if the toxins are easily converted to fat, but I do know that a part of the toxins that we take in from eating meat from mass-fabricated animals could increase your estrogen levels. And besides an high level of testosterone, a good balance between testosterone and estrogen is also an important part of the workings of testosterone.

So even when you’re only a poor college student like me, try to increase the quality of your food intake as your income increaes. Maybe not everything organic at once, but in the Netherlands we have an agency that gives zero to three stars to a animal product that rates the quality of life of the animals. Try to get meats, eggs, diary from sources that had a better life. It could give you a better life and better levels of T and a better balance of T and E too.

13 Drew Mullen January 16, 2013 at 7:36 am

Great article. I am definitely looking forward to tomorrow. Started reading this blog about 1 month ago and I am loving it! thanks.

14 John M January 16, 2013 at 8:30 am

Thanks Brett – definitely enjoying the series so far. Any cholesterol tips for someone that’s unable to eat eggs? Cheers.

15 J.W. Simpkins January 16, 2013 at 8:35 am

I’m glad to see you mention cholesterol as being vital to testosterone production.

With all of the prescriptions being written for statin drugs, it’s no wonder so many men are having low libido issues.

16 Dan January 16, 2013 at 8:57 am

Not to debate the undeniable harm of cigarettes–but in this article they promote T, and in a previous article they lessen T (link below).

Which is it?


17 jwardl January 16, 2013 at 9:51 am

So does this process have something to do with why we tend to get elevated cholesterol levels as we get older, because less of it is being converted to T?

For that matter, which is converted — “good” cholesterol or “bad” cholesterol?

18 Ken January 16, 2013 at 10:42 am

The amounts of steroid hormones is tiny comparing to the total amounts of cholesterol in the body. Not only T, but all other steroid hormones are made from cholesterol. Examples include cortisone, estrogen and progesterone.

Another aspects of T metabolism not discussed here are the conversion of T to DHT, which is responsible for other male characteristics, and is one of the leading cause of baldness in male.

Unless you are some very restrictive vegan diet, I would not worry too much about not having enough cholesterol from a normal North American diet.

19 Jonny January 16, 2013 at 11:07 am

I wonder how your next article or two will align with your past entry on increasing T levels: http://artofmanliness.com/2009/06/03/30-days-to-a-better-man-day-4-increase-your-testosterone/

For example, in the old post it mentions smoking reduces T levels, yet I have been reading the contrary lately.

20 Patrick January 16, 2013 at 11:17 am

Awesome article, Brett!

I’m on the same page as Doc Alexander though. I’m hoping there’s going to be a natural holistic way, in addition to excersize and diet, that will increase my T levels. The whole “Androgel” thing is not that great.

21 Kory Cochran January 16, 2013 at 11:27 am

Great topic and looking forward to the next article in this series. I see health & life insurance in Texas, and I see talk to people all the time that have had “low-T”, and getting it supplemented either naturally or by prescription, has dramatically improved the quality of life for them. I am one of those people too!
Great stuff!

22 Adam January 16, 2013 at 12:06 pm

Ah Ken, you burst my bubble. Here I was hoping Brett was going to recommend increasing our bacon intake!

23 Brett McKay January 16, 2013 at 12:50 pm


Actually, that’s exactly what I’m going to recommend! Adding cholesterol to your diet does help improve T.

24 ken January 16, 2013 at 4:18 pm

I would disagree on eating more cholesterol.

I would assume that most people would eat meat at least 2 if not more meals a day. Along with the gigantic portions that is the usual fare now both dining in and out, I would think that there are plenty of cholesterol to go around.

Aside from bacon and eggs, shell fish and game are both high in cholesterol while being lower in fat. Same as liver. If you feel that bumping up your intake without the fats, those would be excellent sources.

25 Tom January 16, 2013 at 6:02 pm

Great Article Brett ! Looking forward to the next post !

26 Jonathan January 16, 2013 at 6:09 pm

@Smoking_Questioners: Brett addressed the apparent smoking inconsistency in the comments on previous days of this series.
@Brett – Loving this series!

27 Phi Demeter January 16, 2013 at 8:19 pm

These articles have been really good. I have been excited to read each days explanation about “T” and am looking forward to Thursday where you actually let us know what can be done!

28 Cory January 16, 2013 at 8:29 pm


I must have missed that comment. Does smoking help or not?

29 Cory January 16, 2013 at 8:32 pm

Sorry I spelled your name wrong Sir. It was a typo, no disrespect.

30 Charles January 16, 2013 at 9:12 pm

First off, for those who are asking which “form” of cholesterol, HDL or LDL, becomes testosterone; cholesterol is a specific macromolecule which is a component of HDL and LDL. Put simply HDL and LDL are blobs of cholesterol, fats and protein. HDL (high density lipoprotein) is very tightly packed and LDL (low density lipoprotein) is less tightly packed; but they both contain cholesterol, and it is cholesterol which gets converted to the sex hormones (which include testosterone).

Second, and I mean this with all due respect to Brett (I think you have a very good site, I think you do a good job of accumulating background knowledge, you seem like an intelligent man and I think your heart is in the right place), I find a few of the statements made in these past two articles to be towing the line on the kind of information which is inappropriate to be recommended by someone who is not a medical professional. I am not a physician at this point in my life, I am in medical school (which does not yet give me the right to dispense medical advice either).

Just as an example, the sited article which accompanies the comment that “relying too much on cholesterol produced by our nuts (of the non-almond variety) can actually inhibit our Leydig cells from producing T”, has nothing to do with where the cholesterol comes from (synthesized by the liver or from dietary sources); but instead basically says that certain immune cells in the testes (macrophages) produce an enzyme (25-hydroxylase) which can help convert products of cholesterol metabolism into testosterone precursor molecules. Also the testes do not produce cholesterol, in fairness this claim could have just been a typo when he meant liver instead of testicle (and also perhaps the wrong paper was linked). Better links would be the general health information for low T from organizations like the CDC, NIH, or WebMD; the links that have been provided have been predominantly very technical, peer reviewed articles which the vast majority people will not understand.

I want to stress that there are only a few comments that were made in these articles that began to sound like the dispensing of medical advice, but I am a little worried about the articles to come which discuss how to increase your testosterone levels. Low T can be an indicator of some serious medical conditions, and with the above comment of “Actually, that’s exactly what I’m going to recommend! Adding cholesterol to your diet does help improve T” I find myself very concerned about how that could affect someone with low T who already has high cholesterol.

I think it is great that Brett is bringing up such an important subject to men’s health, and that it is opening up discourse not only on testosterone levels but also on the obesity and diabetes epidemics which plague both men and women in the United States. And to Brett; I hope you do not take this as me trying to call you out in public (you do not have a non-public contact that I could find on the site other than twitter or the USPS); but before you tell people how to raise their testosterone by doing things like increasing cholesterol intake, you need to tell them to consult a doctor about the cause of their low testosterone levels and whether the things you’re are recommending to them would be a safe way to treat their medical condition. Dispensing medical advice without medical training to a mass audience is irresponsible at best, and at worst could be deadly.


31 Dick Holms January 17, 2013 at 10:33 am

Does having plenty of sex produce more Testosterone?

And does it matter if done with a partner or just yourself?

Does masturbation actual prevent prostate cancer?


32 Eric January 17, 2013 at 11:08 am

@Charles…Everyone knows he’s not a Dr. & this is not a medical site. He’s simply discussing a topic for people to research on their own. Please don’t try to equate these articles with “dispensing medical advice” because in doing so you are in a sense attempting to censor valuable information.

Your insight as to some of the biology is helpful, but I believe you have become indoctrinated into the medical establishments attitude that only a Dr. should discuss anything to do with health related matters.

Everyone should take charge of their own health and not take a Dr’s. word as absolute. I’ve dealt with more inept Dr’s than I care to recall and if I had taken their advice I’d be a crippled zombie.

Once you realize that the medical profession operates on quotas & mandates from the insurance companies and you get 5 minutes with a patient out of 50 or more that day, it’s easy to see why they keep many people in an endless cycle of problems.

Dr’s serve an important function when it comes to emergencies & saving lives, but (in general) they are abysmal at handilg chronic conditions. They are constrained by too many rules, insurance companies, & let’s not forget Big Pharma….

33 Mike Boston January 17, 2013 at 11:23 am

To Charles et al.:

I am somewhat perplexed by the fairly regular stream of comments to the effect of, “Brett, is not a doctor and should not, therefore, write articles like this one that give health/diet advice.” For example, the following rather dramatic statement was made:

“Dispensing medical advice without medical training to a mass audience is irresponsible at best, and at worst could be deadly.”

The man has never claimed to be anything other than an interested lay person who has done a bit of homework, and at several points during the series he has paused to remind readers of this fact. So my perplexity leads to the question, what would you have him do? Should he simply refrain from commenting on health/diet/fitness related issues, contracting out all such posts to experts in the field? That seems a bit overly restrictive, don’t you think? Surely interested general readers can learn and form opinions and then share with others insights gleaned from their, admittedly, amateur inquiries, can’t they?

~ Mike

34 Alonso January 17, 2013 at 8:55 pm

Loving this articles! And I have to agree with Mike and Eric.

35 Blood Diamond January 19, 2013 at 8:51 pm

Charles, are you sure you’r in med school? You sound as though you should be in law school. Let’s gather coal and give ‘em to Charles, we’ll all be rich.

36 Ek70R January 20, 2013 at 12:13 pm

I only eat egg whites and almost no red meat, but I have a balanced diet consisting of almonds, brown rice, lean chicken breasts salads, olive oil, oats etc etc… and d weightlifting 4 times a week for the last 3 years and a half, and do HIIT cardio on rest days, so….
I suppose I have got high testosterone levels, but in order to have an “optimal” amount of free testosterone should I start eating egg yolks and red meat more often?
PLEASE I wil appreciate any advise!
THANKS BTW really love this site is so awesome!
PS: sorry for my english

37 Brookston John January 21, 2013 at 8:58 pm

I knew it! It’s a plot to de-manify men! “Eat less red meat and eggs but eat plenty of oatmeal to lower your cholesterol!”

I want a big plate of eggs and mountain oysters…

38 clay b February 26, 2013 at 4:48 pm

After my triple by-pass last year my doctors insisted I take a statin drug or I would die. I did a T test 6 months later and found out my T was below the minimum level. I discovered that statins prevent your body from making T and on top of that can cause gynocomastia, i.e. the dreaded man boobs. I decided I’d rather be dead than androganous.

39 S. C. March 24, 2013 at 12:35 pm

My husband started taking statin drugs for high cholesterol 3 years ago. At the time he a very active healthy man. After 2 years, he had leg cramps and ED from the statins and could hardly do anything he used to do. Doctors put him on a more aggressive statin drug, Lipitor. 2 months later he had 2 98% blockages and had angioplasty and stents. At the time of his blockages his cholesterol was normal but his T levels were very below normal as was his vitamin D levels. I truly believe that statin drugs caused all of these problems for him. A healthy heart needs T and vitamin D and the statin drugs depleted his body of both of these. He has been off of statins for a month and is feeling much better and his T levels have increased by more than 50 points just by doing natural remedies. Statins kill you people. Do your research before taking them PLEASE!!!!!!!!!!!!

40 S.C. March 24, 2013 at 12:42 pm

I forgot to mention in the last post that my husband is 39 years old and had his T levels tested two years before taking statins and they were on the upper end of normal. In now way is it normal for a mans T levels to drop more than 50% in 3 years. He also had his pituitary gland tested to rule out any causes of low T and a full urology work up to rule out any prostate or testicle problems all of which came back normal, leaving statins as the only know cause of his low T levels.

41 Joe Perkins March 1, 2014 at 12:50 pm

I have seen some posters here (such as RyanU back in 3/2013) asking about HDL/LDL, cholesterol and testosterone. The cholesterol molecule is simple and composed of a few dozen or so atoms (its formula is C27H46O). HDL and LDL are a protein and several to several dozen cholesterol like molecules bound to that protein. HDL and LDL are one way the body stores extra cholesterol. Like a similar conceptual molecule, glycogen, it is a compound molecule (glycogen being many sugar molecules bound to a protein). Testosterone, like bile acids and vitamin D, is synthesized from a cholesterol molecule. HDL and LDL are a transporter of cholesterol but not the only source of cholesterol. Their levels won’t influence Testosterone synthesis as much as your overall health will.

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