Testosterone & Muscle
Testosterone; it is probably the most discussed hormone in regards to muscle growth in men. I am sure you have heard some person discuss taking testosterone supplements or consuming some super food that will naturally boost testosterone significantly. How much truth is there to the idea of testosterone boosting? Does it have a significant impact? Should you worry about testosterone levels? These are just a few of the questions that rattle around in my head. For some time now, I’ve known the general information on the subject, but once and for all, let us go through the research and identify the truth behind the mighty hormone testosterone.
What is testosterone?
If we are going to discuss something in detail, as I’ve said countless times before, we need to understand what it is first. So, briefly, testosterone is a hormone that both men and women synthesize, and do so due to a precursor hormone known as luteinizing hormone that comes from the pituitary gland. When this hormone is released, testosterone synthesis is activated from the testicles, ovaries, and small amounts from the adrenal glands from a particular cell type called the leydig cells (1)(2).
What does it do?
This is probably not news to you, but testosterone has a wide spread benefit for both sexes, which include, but are not limited to:
- Muscle synthesis
- Bone density
- Deepening voice
- Sperm production
- Fat distribution
Although women produce significantly less (14-20+ times less) testosterone, it is necessary for females to produce testosterone, as well, to reap most of the benefits of the hormone (3).
Types of testosterone?
Now we’re getting deeper into the subject. As with many things related to the body, there are types of of testosterone that get categorized between exogenous (outside of the body) and endogenous (inside the body).
This has little impact on the discussion of testosterone from a health or performance stand point, so I’ll just touch on it, but there are many types of exogenous testosterone. From slow releasing (weeks: Testosterone enanthate, Testosterone cypionate, etc) to fast acting (days: Testosterone propionate, Testosterone phenylpropionate, etc) with different uses depending on type (4). Apart from their intake type (injection, sublingal, gel, etc), these vary based on desired result.
However, later in this article we will see a popular class of testosterone known as testosterone esters (made up of the slow releasing testosterones) used in most of the studies, related to exogenous intake, mentioned throughout this read.
This testosterone is the hormone found from your body’s production, so it is not ingested in any way. There are two types of endogenous testosterone that fall under the umbrella of total testosterone.
Free Testosterone + Bound Testosterone. That’s it – nothing more.
Bound testosterone, as I explained so eloquently above, is one of the two types that make up total testosterone. Bound testosterone is named as such, because it is bound to a few different substances, which are:
1. Sex Hormone Binding Globulin
Originally synthesized in the liver, the direct impact this substance has on the body is still hazy, we do know that it plays a significant role in testosterone (6). As roughly 60% of testosterone in the body is bound to SHBG, this plays a crucial role in figuring out the amount of testosterone we have available to use for various processes (that inevitably help in the benefits listed in “What does it do?” above). Testosterone bound to SHBG is so tightly bound that it is incapable of release into the cells (5)(6)(8).
Also synthesized in the liver, albumin is a spot of controversy as technically, albumin is bound to testosterone, but due to the delicate nature of said bond, the body is able to break it easily enough to then shuttle testosterone into the cells (disclaimer: some consider albumin bound testosterone a free testosterone, not bound)(5)(7). Albumin bound testosterone, however, makes up more than 30% of testosterone in our system (5).
So, to recap, most bound testosterone is not used in the cell, because it is tightly bound, while some can be used in the cell due to its delicate bond.
Free testosterone is, as I’m sure you can guess, free from bondage (down with slavery!) to any molecule and although making up a minority of our body’s testosterone (roughly 2%), it is the part the body uses on the cells (5)(8). Most people want to increase free testosterone in comparison to bound testosterone when they aim to increase testosterone.
Do I need testosterone to build muscle?
Oh, was that not enough?
Okay, yes, testosterone is a huge driving force for protein synthesis, as well as positive effects on nitrogen balance (9), and this is likely a main reason for why testosterone temporarily rises during exercise (10). However, although fundamentally testosterone is undeniably important for the synthesis and retention of muscle, that is not the end of the story.
More must be better, right?
Like many things in physiology, most variables increase directly with the introduction of more of another variable – up to a point. This is readily seen in vitamins, minerals, heart rate, among other areas, and is also true of muscle and testosterone. This is where it is important to understand how, numerically, testosterone increases muscle mass.
Think of testosterone as a range.
If you lie within that range, you will see no significantly better results than someone higher up in that range (11). If you are located below or above that range, there are changes that extend beyond muscle production and retention.
I will not cover everything related to this in this article, but in short, hypogonadism is an underproduction of sex hormone (in this case, testosterone); this can occur due to several reasons (physical damage, genetics, insufficient nutrition, etc)(12). Some of the resulting effects:
Loss of body hair
In this case, a person suffering from hypogonadism that goes through some intervention (Testosterone Replacement Therapy, for example) to increase their testosterone levels would see a reversal in most, if not all, of these negative traits listed above. In this case, an increase in testosterone from below minimum (which is dependent on age) to, at least, minimum test levels would prove beneficial in synthesizing and retaining more muscle (9)(13). This is an example of low testosterone and similar instances that provide a situation for low testosterone would see significant benefit from testosterone intervention (13).
Okay, so we understand that being below normal levels of testosterone and supplementing with testosterone would lead to noticeable changes in regards to muscle, and we also know that if you are already within a normal range in exogenous testosterone, then any small increases would provide no added benefit. Well then, what is the hype about? Why do some drug using athletes use testosterone?
Because supraphysiological amounts of testosterone do have an impact on muscle synthesis. So, a slight increase in testosterone may not do anything, but a massive (3mg/kg/week, or even 600mg total/week) increase in testosterone will have a substantial impact. Subjects given 3mg/kg/week of testosterone, their measured creatinine levels (one way to measure increased kidney work due to muscle metabolism) increased by an average of 20% (14). Likewise, in other studies that used 600 mg of testosterone enanthate (slow releasing exogenous testosterone ester) per week saw the greatest increase in muscle in those that did supplement with training, but also found a significant increase in those who did not train (15). Significant increases in strength were also seen by measures of 1RM (one repetition maximum) ranging from roughly 20% (untrained) to 40% increase (trained)(15).
Again, to recap:
A) Below normal testosterone level + TRT intervention: Significant increase in muscle and strength up to normal ranges.
B) Normal testosterone levels + below supraphysiological dose intervention: No significant increase in muscle or strength.
C) Normal testosterone levels + supraphysiological dose intervention: Significant increase in muscle and strength
What is “normal”?
Normal, in respect to testosterone, is falling inside that aforementioned range. This range changes, primarily, due to age. It is natural to see, in males, a massive increase in testosterone during puberty, and for decades after that point, testosterone remains high.
Total Testosterone, >19 years of age: 240-950 ng/dL (16)
Bioavailable Testosterone, 20-70 years of age (lower end with increasing age): 40-257 ng/dL (16)
Free Testosterone, >17 years of age: 9-30 ng/dL (16)
Total Testosterone, >19 years of age: 8-60 ng/dL (16)
Bioavailability, 20-50 years of age: .8-10 ng/dL (16)
Free Testosterone, >17 years of age: .3-1.9 ng/dL (16)
So, as can be seen, especially in males, the range can be quite broad.
Do I lose muscle as I lose testosterone?
Well, as has been shown in hypogonadism, yes. However, the midlife decline in testosterone (decline of 1% per year) may not be an indicator of lean mass loss throughout aging (19). It is true that muscle is lost with age, but that muscle loss may not be due to testosterone decline, but rather, inactivity (17)(18). I would venture a guess that testosterone is not telling of muscle loss, because a person can be declining in testosterone, but still remain in that “normal” range for the majority of their life.
Are testosterone boosters worth the money?
If you get to this part of the article and do not know the answer already, then either you did not read, did not read carefully, or I am terrible at explaining.
Other than a person suffering from low testosterone relative to normalcy (the range, remember?), and using a prescription grade TRT, or short of getting supraphysiological, pharmacological grade testosterone ester, any other testosterone booster will, with high probability, do nothing for you.
Simply put, testosterone boosters you see on TV, the internet, or at Wal-Mart will do zilch, nada, nothing, rien, nichts, nix for you.
Now we understand that testosterone plays a key role in muscle growth and maintenance, but as testosterone is measured in a range, it does its job well within that range. Anything below that range will prove a lower affinity to muscle and anything above that range will increase muscle and strength, but increasing testosterone within that wide range shows little to no effect. Lastly, testosterone boosters that are not prescription or pharmaceutical grade for testosterone replacement therapy or supraphysiological exogenous intake, respectively, are largely useless.
Written by: Nicolas Verhoeven
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