Six key hormones are responsible for muscle growth; they are testosterone, HGH, insulin, thyroid, cortisol, and estrogen.

It’s easy to take our hormones for granted until they stop performing as they should. A healthy hormone system enables us to stay in shape and conduct our daily activities, but it’s even more important to those trying to gain muscle.

It can be frustrating to dedicate a lot of time and effort to your physique and not see the desired results, yet hormones are rarely thought to be the culprit. With diet and training taking center stage, hormones become an overlooked factor in muscle growth. Here we take a look at the five key hormones that power our muscles and how you can adapt your training techniques for a better outcome.

How do hormones affect muscle growth?

Hormones are vital in regulating our metabolism – the reaction that governs our energy and processes our food intake. During and after a workout, your body is flooded by different hormones which are either anabolic (those that use energy) or catabolic (those that release energy). Only the muscles stimulated during this exercise are subject to the effects of these hormones.

For muscle growth, you need a higher amount of anabolic hormones than catabolic ones. Hormones required for muscle growth include:

  • Insulin;
  • Insulin-like growth factors (IGFs);
  • Growth hormone (GH);
  • Testosterone.

Anabolism enables our muscles to grow because the process involves simple molecules forming together into larger, more complex ones and retaining energy for repairs.

Catabolic hormones, such as cortisol, inhibit muscle growth as the process breaks down molecules and releases energy, for example, food digestion. If there is a higher imbalance of catabolic hormones, you will begin to lose muscle mass.

Any hormonal disruptions, for example, those caused by a thyroid condition, will affect these processes and your overall metabolism. If you’re concerned about a hormone imbalance, or curious what your baseline levels are, our clinic provides a free consultation you can book right away.

#1: Testosterone

The king of all bodybuilding hormones, testosterone (the principal male hormone responsible for building muscle size and strength) promotes the growth of many bodily tissues and is essential for health and well-being. Also produced by women (though 7-8 times less than it is for men), testosterone is one hormone that must be kept elevated in as high a quantity as possible to ensure constant results.

Since the test is essential for increasing protein synthesis to build more muscle at a faster rate, and, considering its influence on keeping growth hormone levels sufficiently high to burn body fat, its depletion will significantly curtail our chances of gaining lean muscle mass.

#2: Growth Hormone (GH)

Growth hormone, which stimulates growth, cell reproduction, and the release of insulin-like growth factor (to boost protein synthesis), is an integral component in supporting fat burning and safeguarding against muscle losses.

As with testosterone, GH production is to be encouraged in healthy trainees. The more, the better. While dieting, many of us lose muscle weight along with body fat; a natural consequence of aerobic training combined with intensive weight training and low fat/low-calorie eating. A drop in muscle may then result in a lowered metabolic rate, and less fat burning. It is therefore essential that we maintain muscle while getting lean, one of the toughest training dilemmas the natural bodybuilder will ever face.

#3: Insulin

Unlike naturally released GH and testosterone, insulin is one hormone that has the potential for doing either great good or much harm. It must therefore be manipulated accordingly. Released in excessive amounts at the wrong times, insulin, produced by the beta cells of the pancreas and central to regulating carbohydrate and fat metabolism, may promote fat storage. Used strategically, however, it may create an anabolic environment to elevate muscle gains and promote fat loss.

In a calorie-controlled pre-contest diet, for example, low insulin levels at rest (between training sessions and, especially, before bed) may assist fat burning while high levels in and around training may promote the rapid uptake into our muscles of amino acids and glycogen, both essential for building more size.

#4: Thyroid Hormone

Primarily responsible for the regulation of our metabolism, the thyroid hormones triiodothyronine (T3) and thyroxine (T4) also support protein synthesis and fat loss. A major problem with all calorie-restricted diets is the concomitant diminishing of thyroid hormone levels. When thyroid levels drop, we experience a corresponding reduction in protein synthesis, calorie-burning, and metabolism, and our gains may begin to stagnate.

#5: Cortisol

While the stress hormone cortisol (a glucocorticoid steroid) may burn body fat, and indeed some bodybuilders deliberately overtrain so as to boost its production to put the finishing touches on their shredding efforts, its effects are mostly negative.

Among its many deleterious actions, cortisol shrinks the thymus gland, a key immune system regulator, thereby signaling immune cells to shut down and die. We may, as a consequence, become more susceptible to various illnesses. Aside from impairing our immune system, cortisol may also promote muscle wastage, fat gain, heart disease, and diabetes, not to mention mood swings, depression, generalized fatigue, and insomnia. Needless to say, cortisol is one hormone that bodybuilders and fitness devotees can all do without.

#6: Estrogen

A hormone produced mostly in females but also to a lesser degree in men (for sperm production and bone maintenance), estrogen (steroidal compounds integral to both menstrual and estrous reproductive cycles) runs counter to bodybuilding and fat loss success. Excess estrogen may even contribute to prostate and breast cancer. Men with a higher body fat percentage are also shown to have elevated estrogen levels.

Affecting the way we look and feel is the body’s testosterone to estrogen ratio: a superior ratio for maximal lean muscle gains would see testosterone production high and estrogen output at minimal levels.

Are your testosterone, growth hormone, and thyroid hormone levels sufficiently high, so as to encourage rapid fat burning and consistent muscle growth? Are your estrogen and cortisol low enough to preclude their combined catabolic effects? Is your insulin under control, increased, or decreased according to your training goals? Answer yes to all of the above and you are well on your way to achieving a head-turning physique to be proud of.

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