Testosterone: The Ultimate Catalyst for Muscle Gain

Consistent resistance training, adequate nutrition, and healthy testosterone levels facilitate increased lean muscle mass.


Celebrity Dax Shepard doesn't mind the attention he's receiving after adding 24 pounds of lean muscle thanks to daily weight training, a high-protein diet, and testosterone replacement therapy (TRT). But "forget the body," he explains. "Mentally, I love it because it makes me far more on fire to be alive. I was depressed. I was retiring; that was the plan. This is the version [of myself] I enjoy." According to Dax, low testosterone (T) runs in his family. He has battled addiction and depression for most of his life but can generate positivity since starting TRT.

Benefits of adding lean muscle

Losing fat and gaining lean muscle not only improves your appearance but improves your overall health. There are several benefits of adding lean muscle mass, including:

  • Support for bones and joints.
  • Improved balance and mobility–As muscle mass increases, balance improves, reducing the risk of falls and injuries.
  • Weight loss–Metabolism is enhanced as muscle increases, making it easier to burn more calories, even at rest. Strength training can significantly help reduce body fat and increase lean muscle.
  • Lowered blood sugar–Increased muscle mass helps the body store more glycogen in your muscles, which aids in blood sugar regulation.
  • Prevents cognitive decline–Regular strength training may help improve cognitive function and learning ability and prevent age-related mental degeneration.

What Does This Have to Do With Testosterone?

Testosterone (T) is an androgenic sex hormone secreted by the Leydig cells in the testes in response to hormones produced in the brain. Testosterone has many functions, including primary sexual development, mental and physical energy maintenance, and blood sugar regulation. In addition, T regulates secondary sexual characteristics such as vocal changes, voice deepening, anabolic effects, and skeletal muscle growth. Testosterone levels start decreasing around age 30, causing a decrease in libido, bone density, muscle mass, and increased body fat.

Many current studies agree that T supplementation increases muscle mass in hypogonadal older men with low or low-normal T levels and men with chronic illnesses.  In addition, T's anabolic effects on muscle mass and size are dose and concentration-dependent

The mechanisms by which T increases muscle mass are not fully understood but appear to be related to:

  • Increased protein synthesis.
  • Increases in satellite cells and fusion of satellite cells with muscle fibers increase the myonuclear number and muscle hypertrophy.
  • Changes in satellite cell ultrastructure.
  • Binding to androgen receptors, followed by nuclear translocation and gene regulation.
  • Increasing growth hormone.

Minor increases in T levels may be obtained naturally, with:

  • Resistance exercise.
  • Protein and carbohydrate consumption. 
  • Stress reduction-high long-term stress increases the stress hormone cortisol, which disrupts T production.
  • Sun exposure- sunlight increases T production.
  • Increased activity.
  • Limited alcohol consumption.

Testosterone replacement therapy is indicated for the treatment of hypogonadism. Male hypogonadism affects 10–30% of the population and is under-recognized and undertreated. Benefits of TRT include improved erectile function and libido, lean body mass, and bone mineral density.

Muscle Metabolism – The Importance of Feeding Your Muscle

Muscle influences energy and protein metabolism throughout the body. In addition, skeletal muscle is the primary site for glucose uptake and storage and is a reservoir for amino acids, stored as protein. 

Muscle mass increases when the net protein balance is positive: muscle protein synthesis (MPS) exceeds muscle protein breakdown (MPB). More specifically, muscle mass increases as small amounts of protein accumulate in response to resistance training, adequate nutrition intake, and other factors. 

Under normal circumstances, muscle gains and losses during fed and fasting states negate one another. When the body's energy demand exceeds protein consumption, amino acids are redirected from skeletal muscle. For example, muscle wasting can occur due to illness associated with loss of appetite and increased energy demand. 

Protein intake is critical to building muscle. The Academy of Nutritional and Dietetics recommends that the average individual consume between 0.8 and 1.5 grams of protein per pound of body weight. Men should consume this amount of protein in 4 to 6 servings spread across the day. However, daily protein intake seems to be the most critical variable, rather than specific pre-or post-exercise timing considerations. 

Protein demand increases as we age. For example, around 50 years of age, we need to increase the protein in our diets to maintain muscle mass. Protein supplementation has been shown to improve muscle building along with regular resistance training. However, a diet based on the current protein intake recommendations can be achieved through a balanced diet and does not require additional supplementation.

Proteins consist of one or more chains of amino acids known as polypeptides. Of the 20 amino acids, some can be synthesized in the body, but others, known as essential amino acids, must be obtained from the diet. Some debate has been about whether consuming amino acid supplements enhances muscle gain. However, there does not appear to be a benefit in consuming free amino acids over intact proteinCurrent studies suggest intact proteins such as eggs, whey, beef, and soy illicit an anabolic response similar to or greater magnitude to free-form amino acids.

Shock Your Muscle to Stimulate Growth

To maximize muscle hypertrophy, we must increase our muscles' mechanical tension. Increased resistance exercise damages the muscle fibers, but in a good way. The body repairs the damaged fibers by fusing them, which increases muscle mass and size. 

Muscle building can be augmented by:

  • Using proper form and execution.
  • Tempo-lifting.
  • Maximizing the mind-muscle connection.
  • Stretch and squeeze during repetitions.
  • Taking the exercise to muscle failure.
  • Using repetition variations.
  • Performing the movement in the full range of motion.
  • Utilizing progressive overload.

Satellite cells play a central role in muscle growth, maintenance, and repair. Numerous satellite cells throughout the muscle are stimulated to divide when the muscle is damaged. Satellite cells are activated in response to muscle injury, causing them to multiply and become myoblasts, then myocytes, which fuse to form myofibrils. In addition, increased T is associated with more satellite cells. Skeletal muscles consist of long, tubular muscle fiber cells, which contain many chains of myofibrils. 

In addition to increased satellite cells, increased myonuclei are also related to muscle hypertrophy and increased T. The satellite cell structural changes are also associated with increased T and muscle hypertrophy.

Skeletal muscles can adapt to changes in contractile activity and nutritional intake. For example, resistance exercise stimulates muscle protein breakdown (MPB) rates and more remarkable muscle protein synthesis (MPS). Hypertrophy occurs with repeated alternating of resistance exercise with protein ingestion, resulting in the gradual accumulation of skeletal muscle protein. When protein is ingested along with resistance exercise, rates of MPS are stimulated over and above those of MPB.

A study found that one 30-minute weightlifting session increased T levels by 21.6% in men. Another study demonstrated that men who did resistance training three days per week were linked to increases in T levels right after the workout and over time. The T increase from resistance training shows a significant degree of individual variability. Whether this post-exercise increase in T concentrations impacts the extent of muscle anabolism and hypertrophy is widely debated. 

Muscle growth occurs at different rates depending on age, sex, and genetics. In addition, muscle growth increases when exercise is consistent, challenging, long-term, and followed with enough rest. If there is insufficient rest between resistance training workouts, the muscle group cannot repair, fitness progression and muscle growth are slow, and the risk of injury increases. Also, the same muscle groups should not be challenged on two consecutive days.

Heritability of Skeletal Muscle Traits

Current studies are revealing the impact genetic factors have on muscle traits. For example, several studies have estimated the heritability of grip strength between 30 and 50%. In addition, recent twin studies found heritability for muscle strength ranging from 30 to 85%. In another twin study, lean body mass was reported to be 80% heritable

Studies show that T levels in men and women have about 20% heritability and are influenced by the combined effects of several genetic variants and genes. In men, high levels of inherited T were beneficial, such as reducing the risk of diabetes mellitus. In contrast, high testosterone in women was detrimental, increasing the risk of many hormone-sensitive cancers and metabolic disorders.

TRT Can Help Prevent Muscle Atrophy in Men Unable to Exercise

Numerous studies have confirmed the correlation between low T and frailty in men. Randomized studies support the benefits of TRT on muscle volume and strength among men with low T levels. Results of a study suggest that T therapy may help retain muscle in men with limited mobility who cannot exercise. 

Testosterone therapy improved insulin resistance, glucose metabolism, and body composition in frail men with mobility issues and testosterone deficiency. These changes resulted in improved physical function and improved overall quality of life. The study suggests it is warranted to explore the potential usefulness of T treatment to counteract and slow the progression of muscle loss for men unable to exercise.

It is more difficult to increase muscle with age. To make matters worse, most men start losing muscle around age 30 and lose 3–5% of their muscle mass per decade. While the decrease in muscle can be lessened through resistance training and proper nutrition, decreased testosterone levels make it more difficult. If building or retaining muscle has become exceedingly difficult, or you are experiencing other symptoms of hypogonadism, a medical evaluation may be in order. Mainstream medicine is finally beginning to recognize the importance of having healthy T levels.

Marius and its logo are registered trademark of Marius Pharmaceuticals LLC. This website is intended for US residents only and is not a substitute for medical advice.
© 2023 Marius Pharmaceuticals. All right reserved.