Updated: Feb 19
Testosterone is one of the most important hormones in the male body, it also one of, if not, the most abused anabolic steroid on the planet, able to increase muscle mass and strength rapidly.
But what makes this steroid so powerful?
What Is Testosterone?
Testosterone, which comes in many esters such as; Testosterone Enanthate, Testosterone Cypionate and many others is a form of steroid in the androstane class containing a keto group at the three position and hydroxyl group at the seventeen position.
It is synthesised in the body via several steps from cholesterol and is converted in the liver to its metabolites. It exerts its action through binding to and activation of the androgen receptor.
In humans and most other vertebrates, Testosterone is primarily secreted by the testes in males and, to a lesser extent, the ovaries in females.
Levels of Testosterone in the average male are about 7-8 times as great as in females.
Because males metabolise Testosterone faster than females, the daily production of Testosterone is about 20 times as much as females.
Anabolic steroids, such as Testosterone, have two classes of effects, these are anabolic and androgenic. Anabolic means to build up/create, androgenic means male attributes and characteristics.
Growth of muscle mass
Improved bone density and strength
Stimulation of linear growth
Maturation of sex organs
Growth of facial hair
Growth of body hair
Deepening of the voice
Promotion of other secondary sex characteristics
Testosterone has many significant effects during all different stages in life, such as those before birth, during infancy, before and during puberty and also in adults.
Because these aren't relevant to muscle growth they wont be discussed in detail but Testosterone is so powerful it determines the sex of a baby before it is born.
Effects in Adult Males: (most likely correlates to younger males & also females)
Increased red blood cell production
Increased bone density and strength
Increased muscle mass and strength
Increased facial and body hair growth
Modulates fat mass distribution
Modulates cognition and mood
Modulates sexual function and desire
Necessary for normal sperm development
May cause acne
May promote prostate growth and cancer
May promote sleep apnea
May promote infertility
May promote blood clots and strokes
May promote heart disease and heart attacks
May promote male pattern baldness
May promote gynecomastia
This is all well and good to know but what your really wanting to know is how effective Testosterone is at building muscle.. well i'll explain all of the biological effects it has on muscle and its real world research right now!
How Does Testosterone Increase Muscle Mass?
Firstly, lets see how good Testosterone is at building muscle mass.
One study with 43 men placed into four groups; placebo + no exercise, placebo + exercise, Testosterone + no exercise, Testosterone + exercise, the Testosterone (Testosterone Enanthate) was given as an intramuscular injection at 600mg per week for 10 weeks.
As you have probably guessed, the Testosterone + exercise group had the most significant changes in muscle mass at 6.1kg (13.4lbs) +/- 0.6kg, even the Testosterone + no exercise group outperformed both placebo groups in muscle mass changes.
Testosterone Increases Muscle Mass Without Training:
There are multiple studies showing similar results in muscle mass growth but what actually is causing this muscle growth?
Testosterone, primarily through activation of the androgen receptor (AR), induces Akt/mTOR/FOXO3-mediated growth of muscle mass.
In one study, 3mg/kg/bw (3mg per kg of bodyweight) on normal male subjects increased muscle protein synthesis in all subjects with a mean increase of 27%, along with a mean decrease in leucine oxidation by 17%, whole body protein synthesis was not altered significantly.
Testosterone May Increase GHRH And Growth Hormone:
Testosterone administration to pubertal boys increased mean spontaneous Growth Hormone secretion from 2.25mcg/L before Testosterone administration to 6.77mcg/L after administration of Testosterone.
However it seems that this increase in Growth Hormone was mediated via an estrogenic pathway and not directly the cause of Testosterone.
During a study comparing 300mg per week, of either Testosterone Enanthate (TE) or Nandrolone Decanoate (ND), Growth Hormone levels trended towards an increase in the TE group from 1.23ng/ml to 3.3ng/ml, whereas in the ND group they remained unchanged, Estrogen increased significantly in the TE group (by 193.04pmol/L) but decreased (by 50.65pmol/L) in the ND group, leading to the same conclusion that Estrogen must have a role in increasing Growth Hormone.
Testosterone May Increase IGF-1:
Testosterone also significantly increases IGF-1. Serum IGF-1 levels increased after 6 Weeks of Testosterone Enanthate (TE) at 300mg per week but did not change in the Nandrolone Decanoate (ND) group, however, the level of major IGF-Binding Proteins was decreased in the ND group.
Testosterone Could Decrease Myostatin:
Androgens, such as Testosterone, may have an impact on Myostatin within skeletal muscle, in one rat study assessing Myostatin levels in the levator ani (LA) muscle of rats after castration, with Testosterone replacement found Myostatin return to baseline and without Testosterone replacement, active Myostatin proteins were observed to increase.
Testosterone Increases Muscle Cell Hypertrophy:
ERK1/2 and Akt showed an increase in phosphorylation after Testosterone stimulus at 5 Minutes and 15 Minutes respectively. S6K1 was phosphorylated at 60 Minutes.
This response was abolished by PI3K/Akt and mTOR inhibition but not by ERK1/2 inhibition. CSA increased at 12 Hours and was abolished by inhibitors of the PI3K/Akt pathway as well as by AR inhibition.
Testosterone Increases The Appetite Hormone:
One last thing that most people forget about is appetite, this is what allows you to eat and consume enough calories, protein and other nutrients to support muscle growth.
As you should know, nutrition is the determining factor in how fast and how much you can grow.
Testosterone in some studies, such as this one below, has shown a strong positive correlation of Testosterone and Ghrelin, but also a correlation with Estrogen, it seems as Testosterone and Estrogen increase the level of Ghrelin also increases, which also explains the increase of other anabolic hormones, such as, Growth Hormone and IGF-1.
Ghrelin is also naturally higher in females, making it even more likely that Estrogen also plays a role.
So it seems Testosterone is a very interesting and powerful hormone when it comes to its effect on the body and increasing muscle mass and strength.
It is not controversial that Testosterone does in fact increase muscle mass and may decrease body fat.
However it does come with its downsides and may even, with extended periods of abuse using exogenous steroid hormones, contribute towards fatal side effects.
Caution: We strictly do not advise anyone to use, or consider using, any exogenous hormone or chemical such as Testosterone.