Testosterone & Myostatin Levels Effect on Muscle Gains

August 8th, 2010 by Paul Johnson

When people think about muscle building and what in the body helps muscle gains they usually just think of testosterone. Testosterone is a very important muscle builder, in fact its probably the most important factor. That is why women generally can't build muscle as well as men naturally, unless they take steroids, to get a artificial source of testosterone. There is other hormones that interact with testosterone and others that are unrelated that affect muscle growth like myostatin.

Testosterone impact on muscle growth

Testosterone as most bodybuilders know increases protein synthesis by attaching itself to the androgen receptors on the muscle. One important thing most don't realize is it also simultaneously blocks cortisol. It allows you to avoid over training more and not have to worry about muscle breakdown from high cortisol. That is why guys on steroids can workout longer and more frequently and have faster recovery. Natural bodybuilders need to do the opposite and keep workouts short and volume and frequency low.

Another mechanism people don't realize that testosterone does is it stimulates a thing in the muscle cells called satellite cells or myonuclei. These are the powerhouse centers inside the muscle cells. As you will see in studies I give below, the muscle fibers need a certain amount of myonuclei before they grow. So if testosterone isn't there to stimulate the growth of new myonuclei, then your muscle gains will plateau.

Patrick Arnold, an expert on steroid physiology, has alluded to this powerful effect of satellite cells from testosterone / steroid use. He also theorizes it may lead to more permanent muscle gains via hyperplasia (formation of new muscle fibers). Hyperplasia has been a hot debate in the bodybuilding community, but there is evidence that testosterone can play a crucial role in it.

Here is a study that supports Patrick Arnold's theory of steroid use on increased satellite cells and actually the growth of new muscle fibers. Even though this blog advocates natural use an no steroids, studies on steroids often help us understand how hormones like testosterone work on muscle growth.

Med Sci Sports Exerc. 1999 Nov;31(11):1528-34.

Muscle biopsies were obtained from the trapezius muscles of high-level power lifters who have reported the use of anabolic steroids in high doses for several years and from high-level power lifters who have never used these drugs.

RESULTS: The overall muscle fiber composition was the same in both groups. The mean area for each fiber type in the reported steroid users was larger than that in the nonsteroid users (P < 0.05). The number of myonuclei and the proportion of central nuclei were also significantly higher in the reported steroid users (P < 0.05). Likewise, the frequency of fibers expressing developmental protein isoforms was significantly higher in the reported steroid users group (P < 0.05). CONCLUSION: Intake of anabolic steroids and strength-training induce an increase in muscle size by both hypertrophy and the formation of new muscle fibers. We propose that activation of satellite cells is a key process and is enhanced by the steroid use. The incorporation of the satellite cells into preexisting fibers to maintain a constant nuclear to cytoplasmic ratio seems to be a fundamental mechanism for muscle fiber growth. Although all the subjects in this study have the same level of performance, the possibility of genetic differences between the two groups cannot be completely excluded.

The study below showed that preventing activation, proliferation, and/or differentiation of satellite cells seems to stop hypertrophy.

Phelan JN, Gonyea WJ. Effect of radiation on satellite cell activity and protein expression in overloaded mammalian skeletal muscle. Anat. Rec. 247:179-188, 1997

Irradiation may prevent hypertrophy by impairing activation, proliferation, and/or differentiation of satellite cells. Small fibers in overloaded muscle appear to be new fibers arising from satellite cells. IGF-I may have a role in muscle hypertrophy involving satellite cell activation, or perhaps a more direct role that requires additional factors

Study below shows evidence that during hypertrophy the number of myonuclei increase proportionally to the increase in fiber volume

J Appl Physiol. 1999 Aug;87(2):634-42.

The effects of 10 wk of functional overload (FO), with and without daily treadmill endurance training, on the cross-sectional area, myonuclear number, and myonuclear domain size of mechanically isolated single fiber segments of the adult rat plantaris were determined.

All fiber types in both FO groups had a significantly larger (36-90%) cross-sectional area and a significantly higher (61-109%) myonuclear number than did control. The average myonuclear domain size of each fiber type was similar among the three groups, except for a smaller domain size in the type IIx/b fibers of the FO compared with control. In general, these data indicate that during hypertrophy the number of myonuclei increase proportionally to the increase in fiber volume. The maintenance of myonuclear domain size near control values suggests that regulatory mechanisms exist that ensure a tight coupling between the quantity of genetic machinery and the protein requirements of a fiber.

Bodybuilders with higher natural testosterone levels may have more muscle fibers due to hyperplasia. Boosting testosterone naturally may help induce this too.

Other hormones working with testosterone to build muscle

IGF-1 seems to be a potent hormone that works in conjunction with testosterone to increase protein synthesis and satellite cell activation. Postworkout there is a huge spike in IGF-1 and many believe this helps activate the protein synthesis increase we see for about 24 hours post workout. When testosterone levels are high IGF-1 tends to be high and when they are low so is IGF-1. Estrogen actually helps anabolism too. Estrogen is a natural byproduct already from the conversion of testosterone to DHT and estrogen. Growth hormone also seems to help muscle building. Growth hormone doesn't seem to build much muscle on its own. Most bodybuilders suggest that growth hormone works together with testosterone to build muscle.

Myostatin studies on muscle growth

Myostatin levels is more ingrained into your genetics. Its not something that fluctuates based on many lifestyle factors like testosterone. Unfortunately, it does play a big role in muscle growth. Rats that were able to have this gene removed grew to freak size muscularity.

This study showed that myostatin declined a lot post excercise. Remember that a myostatin DECLINE means that muscle growth becomes easier because the higher the levels of myostatin the more it inhibits (slows) muscle growth.

Med Sci Sports Exerc. 2004 May;36(5):787-93.

We determined and compared the magnitude of changes in resting plasma myostatin and IGF-1, muscle strength, and size in response to whole body or local muscle resistance training in healthy men.

RESULTS: In subjects of both groups, elbow flexor 1-RM and cross-sectional area increased (P = 0.05) by 30 +/- 8% (mean +/- SD) and 12 +/- 4%, respectively. Individual changes in myostatin ranged from 5.9 to -56.9%, with a mean decrease of 20 +/- 16%, whereas IGF-1 did not change from pre- to posttraining. There were no significant differences in any of the responses of the subjects between the two training programs. CONCLUSION: Myostatin may play a role in exercise-induced increases in muscle size, its circulating levels decreasing with resistance training in healthy men.

The study below says that myostatin mrna declined during weight loss. This may help as a way to help avoid too much muscle wasting during weight loss.

J Clin Endocrinol Metab. 2004 Jun;89(6):2724-7.

Myostatin mRNA levels result clearly decreased after weight loss, suggesting a role in counteracting the progressive decline of muscle mass after BPD. Myostatin may provide therefore another mechanistic explanation for the control of energy partitioning between protein and fat, working against muscle wasting. Our data suggest that myostatin might represent an important regulator of skeletal muscle size also in conditions of food restriction in obese subjects.

How to change natural testosterone and myostatin levels

Testosterone levels are easy to boost naturally via a high calorie surplus. Studies show that eating a high calorie surplus boosts your testosterone, IGF-1 through the roof. Eating plenty of fats helps maintain or increase testosterone too. Getting a healthy amount of saturated fat and monounsaturated fats really helps boost testosterone. Polyunsaturated fat doesn't have that effect, it actually works against you, so don't eat too much of your fat from polyunsaturated sources. You should try to get plenty of fats while bulking or dieting to help maintain testosterone levels. There is many studies that show high fat diet helps boost testosterone. One thing I will say though if your already eating a large calorie surplus the fat boost probably won't be existent. Calorie surplus already increase testosterone dramatically, so you probably can't boost it any higher just by increasing the amount of fat you intake together with a calorie surplus.

There is also studies showing colder weather, lack of quality sleep, stress, and alcohol lowers testosterone. There isn't much evidence on how to manipulate myostatin levels naturally, other than the studies I gave. It seems to fluctuate based in response to your weight training and dieting. There are some myostatin blocking supplements you could try to manipulate your myostatin levels.