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  • Writer's pictureGavin Guard, Medical Director

What causes low testosterone and what to do about it

Updated: Jan 23, 2022

Key Takeaways

  • Low testosterone is a very common condition

  • Taking testosterone replacement therapy should NOT be the first-line treatment for most men

  • Many factors affect testosterone production including stress, body fat, blood sugar imbalances gut health, thyroid hormones, inflammation, history of concussions, etc.

  • Use diet, lifestyle, and functional medicine to get down to the root cause of low testosterone levels

Vanishing Men

Are men these days becoming less “manly”? Research is suggesting so and at an alarming rate.

Testosterone is the main hormone that makes men “men”, and it has a lot of health impacts when its levels are tanked. Check out these excerpts from some recent studies.

“1 in 4 American men over the age of 30 have clinically low testosterone” (Araujo et al)

“The sperm counts of men in at least 21 countries, including the United States, have decreased by about 50 percent since 1938” (Sakkebaek et al)

“A 35 year old male in 2005 had about 20 percent less testosterone than a man of his father’s generation of the same age” (Antti Perheentupa, MD, PhD)

“A 65-year old man in 2014 will, under typical circumstances, have testosterone levels that are 15 percent lower than a 65-year old man in 1999” (Travison et al.)

Pretty crazy, right?

You may see why so many people are reaching out to male health clinics to get on testosterone replacement therapy (TRT). However, many clinicians are too quick to put people on TRT. Even the Journal of Clinical Endocrinology says, “Lifestyle measures should attempt to raise testosterone before hormone replacement therapy”. How many clinicians actually do this before putting someone on TRT? Furthermore, how many clinicians actually understand the interconnecting relationships between other factors in the body that affects testosterone?

In this article I am going to give you information about what causes low testosterone and what to do about it.

How testosterone is made

First, let’s take a quick dive into testosterone production and release. There are two major ways your cells communicate with one another in the body. The first is the neurologic system and the second is the hormonal system. Hormones are either proteins or steroids that travel through the blood to affect other cells in different organs, neighboring cells, or the cell that released the hormone.

Testosterone is a steroid/androgen hormone produced from cholesterol (more on that later). When it reaches its target cell, it attaches to the androgen receptor on the cell membrane. This receptor/testosterone complex then gets shuttled into the nucleus of the cell where it exerts its effects mainly through stimulating the “activation” of certain genes and proteins in the cell.

How the brain affects testosterone production

Like most hormones, testosterone levels are regulated by the brain. Part of the brain called the hypothalamus releases gonadotropin releasing hormone (GnRH) in a pulsatile fashion every 1-2 hours. The half-life of this hormone is only 2-4 minutes, so never try measuring it unless you want someone to stick a needle in your back.

GnRH then tells the pituitary to release two other hormones; follicle stimulating hormone (FSH) and luteinizing hormone (LH). FSH travels through the blood to tell the sertoli cells in the testicles to produce sperm. Testosterone also tells the Sertoli cells to make sperm. 90% of the cells in the testes make sperm, not testosterone.

how the brain affects testosterone production

LH’s job is to tell the Leydig cells to produce testosterone. It’s probably no surprise that testicles are the organs that produce testosterone (95% of total testosterone), but what some may not know is that the adrenal glands (the hat-shaped organs that sit on the kidneys) produce the other 5% of total testosterone.

Long-story short is that the brain is the epicenter for where testosterone production begins. Things like concussions can lower testosterone output.

Testosterone transport

Once testosterone is made, it travels through the bloodstream via 3 main mechanisms. 66% (⅔) of total T attaches to a protein called sex hormone binding globulin (SHBG). Most of the T attached to SHBG is “unavailable” to cell receptors. However, there is a question whether a receptor complex called “megalin” (kind of sounds like the dinosaur) can engulf this SHBG-T complex; this is super cool.

The other ⅓ is attached to a protein called albumin and is available to cells.

The other 1-2% is called “free T” and is not attached to carrier proteins. This free T is the main portion of total testosterone that exerts its role on cells throughout the body.

What does testosterone do?

I think we all know what sperm do. Testosterone on the other hand has many effects throughout the whole body. Testosterone:

  • “feeds” our frontal lobe of our brain to assist in cognition

  • drives libido

  • mediates muscle and bone growth

  • stimulates an enzyme that breaks down lipids in our blood stream

All of these factors tie into the fact that testosterone helps us get strong and put on lean body mass.

How testosterone replacement can shut down natural testosterone production

The main regulator of testosterone secretion is testosterone itself. So, the more testosterone you have, the less your body will make. This is called “negative feedback”.

You can start seeing the problem here if you consider what happens when you give an individual testosterone replacement therapy (TRT). Exogenous (not made from the body) testosterone is going to shut down the whole system at the level of the brain. Why would your body produce more testosterone if it already has enough?

How thyroid hormone affects testosterone

The three main hormone systems in the body are cortisol (stress hormone), thyroid hormone, and sex hormones. These 3 systems have a very intimate relationship with one another. If one is off, it can throw the other two off. The system that is frequently “off” is the thyroid system. Mostly, this is due to the gut’s powerful influence on thyroid production, synthesis, and conversion- and many people have gut issues.

Thyroid hormone is the main factor that dictates cholesterol getting into the mitochondria to make testosterone. In other words, thyroid hormone is required for testosterone to be produced from cholesterol. We now see a connection between low thyroid and low testosterone.

How stress affects testosterone production?

Stress inhibits testosterone production at the level of the brain. Cortisol is our major stress hormone. When cortisol is chronically elevated (overtraining, psychological stress, physiological stress), cortisol shuts down the testosterone system at all levels (hypothalamus, pituitary, testes). Cortisol also reduces androgen (testosterone) receptor sensitivity- “oh crap”. Your body isn’t worrying about getting huge if you are in a fight or flight state.

To make things worse, stress and cortisol also affect thyroid. In fact, cortisol reduces the conversion of the inactive thyroid hormone (T4) to the active form (T3). This is another way of how stress can impact your hormone levels.

This makes sense as your body is not concerned with muscle growth and making babies when you are stressed out- that’s not its top priority. To put it simply, both stress and thyroid hormone affect testosterone production, transport, and sensitivity at the site of the receptor. Thus, keeping your thyroid levels in check and stress managed can positively affect testosterone levels.

How body fat stress affects testosterone production?

Healthy levels of body fat have a positive effect on testosterone production. However, it’s important to know that your body fat is actually an organ. Body fat actually produces hormones and can be pro-inflammatory. Furthermore, body fat contains an enzyme that actually turns testosterone into estrogen. This means that’s important to maintain a lean amount of muscle mass and work to decrease high amounts of body fat.

How inflammation affects testosterone

Inflammation is another factor that can shut down testosterone production at the level of the brain and testicles. Furthermore, chronic inflammation turns on the sympathetic nervous system (fight or flight) which further activates a suppressive effect on testosterone production.

Inflammation can be due to chronic infections, gut imbalances, overeating, high levels of body fat, blood sugar imbalances, joint degeneration, and food sensitivities to name a few.

How medications affect testosterone

Many medications also carry side effects that can mess with testosterone production. One of the major side effects of antidepressants like SSRIs is sexual dysfunction (low libido and erectile dysfunction). This is because SSRIs have a negative effect on testosterone production at the level of the brain.

GABA is another neurotransmitter that can throw off testosterone when altered with medications such as alcohol, benzodiazepines, and marijuana. GABA seems to be an androgen receptor antagonist and an appetite stimulant.

Other medications such as Adderall which create surges of dopamine in the brain. I’m not suggesting everyone with low T get off these medications, but I think it’s imperative to understand that they COULD be a reason for low testosterone.

How blood sugar control affect testosterone

Finally, let’s talk about how blood sugar imbalances and diabetes can cause low testosterone. Low T is one of the first biomarkers of diabetes. As mentioned before, increased fat tissue carries aromatase enzyme which converts testosterone into estrogen. Blood sugar imbalances also cause inflammation which shuts down testosterone production.

Thus, it’s important to get a comprehensive evaluation of blood sugar balance and work to control it using diet, lifestyle, and functional medicine.

How exercise affects testosterone

Now let’s look at how training/exercise affects testosterone levels and how this affects our ability to get stronger.

I vividly remember a coach who told me that I should do more deadlifts to increase my testosterone levels. I was hooked on the idea, so I did more deadlifts from his advice. In the strength and conditioning field, there are training programs specifically designed to target hormones such as testosterone. This makes sense at surface level but how much does testosterone really play in gaining muscle mass?

Resistance training causes acute rise in testosterone

It’s quite apparent that resistance training creates an acute spike in testosterone and other hormones such as growth hormone. There’s no doubt about it!

Some attribute hypertrophy (more muscle mass) to these changes in hormones- this is called the “hormone hypothesis”. However, we have to ask does this lead to long-term changes in testosterone levels and how much this change really matters?

Do these acute changes matter?

These acute increases in testosterone level post-exercise don’t really make a difference when considering putting on muscle. The acute increases in testosterone and growth hormone usually go away within 30-60 minutes after resistance training. There is a question that this acute rise of these growth hormones may be at least partly caused by a brief period of dehydration that causes relatively higher levels of testosterone after exercising.

The “Doctor of Muscle”, Dr. Brad Schoenfeld, states, “My take based on the current body of evidence: While I can’t dismiss that acute hormonal elevations may play a role in the growth process, I’m quite confident in saying that if such an effect does in fact exist, it would be of small consequence.”

Does this lead to long-term change?

Even though resistance training leads to acute spikes in testosterone, doing too much intense exercise can actually lead to decreases in testosterone. This is especially true in endurance athletes. This is due to the stress response.

What drives muscle growth (hypertrophy)?

So, if it’s not testosterone and growth hormone mediating these changes in muscle growth, then what is. Hypertrophy is a matter of balance between muscle protein synthesis (production) and muscle protein breakdown. When it comes to these two, it looks like muscle protein synthesis (MPS) is the lynch pin, meaning that it has the most say in the outcome of net growth or breakdown. However, if you are an endurance athlete who puts on 50 miles of running a week, it’s usually a matter of reducing muscle protein breakdown that will be the major dictator of net muscle growth.

So, if MPS is the major player in hypertrophy, what affects MPS? Mechanical tension through the system is going to be the main driver of MPS, along with creating heat and acidity.

Dr. Pat Davidson says, “It seems as though the combination of mechanical load, heat, and acidity is the right environment for optimizing muscle growth. The research in this area seems to indicate that multiple sets (3-5) of approximately 10 repetition maximum (RM) load using multi-joint compound exercises (squatting, bench pressing, deadlifting, pull-ups) with short rest (approximately 60 seconds) is optimal for increasing muscle mass.”

This means it’s more of a matter of creating a chaotic cellular environment in your muscles that drives long-term adaptation (not more and more testosterone).

Thus, hypertrophy is not a matter of acute fluctuations in hormones, but rather a change in environment that leaves your muscles nowhere to go, but to adapt and grow. Interestingly, hypertrophy can occur in the ABSENCE of anabolic hormones.

Testosterone and growth hormone are important for hypertrophy but probably not as important as you might think. We discussed how acute changes of anabolic hormones within normal ranges (not taking testosterone replacement therapy) plays little role in hypertrophy and thus, training programs solely designed to create a “testosterone stimulation” don’t have much merit.

Testosterone levels are not a bench press number

Levels of testosterone are not a bench press number- more doesn’t always mean better. However, changes over time of testosterone do have a role in how much progress one makes in the gym. For example, a guy who usually sits at 800 ng/mL (on the higher end of normal) and drops down to 500 ng/mL (still within normal) may be feeling the affect of this change (low libido, loss of muscle mass, poor cognition) when compared to someone whose testosterone is 400 ng/mL and has not changed.

The Bottom Line

In this article, I talked about what causes low testosterone and what to do about it. I also examined the role of exercise and testosterone.

If you got anything out of this article, I hope you realized the impact of taking testosterone replacement therapy. If you are on TRT for a long period of time, your body may shut down natural testosterone production for good.

I hope you found this information useful and helpful in your journey back to a healthier and happier life.

Like what you are reading? Learn more about how to take control of your health by signing up for the "5 Minute Health Makeover" below where I coach you through 3 pivotal strategies for better health.


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