Most important hormones for muscle growth and tips on how to improve them

For those of you who seem to struggle with gaining muscle and just get fat instead, or if you’re one of those people who just struggle to gain any weight at all, I trust that this post can be of some help to you.

First and foremost I’ll be discussing the thyroid as your thyroid is extremely important for muscle growth…



Thyroid hormones increase and activate satellite cells in the muscles, increase myogenic (muscle growth) factors, lower myostatin (a negative regulator of muscle growth), convert slow twitch muscle fibers to fast twitch muscle fibers, increase steroidogenesis, increase cortisol excretion from the body, increase follistatin (positive regulator of muscle growth), increase IGF-1 levels and IGF-1 availability, and also increase the metabolic rate.

So as you can tell, thyroid function and thyroid hormones are crucial for anabolism.

Things that inhibit thyroid function are nutritional deficiencies, inflammation, gut-irritating foods (increase inflammation, endotoxins, prolactin, estrogen and serotonin which are all thyroid antagonists), serotonin, cortisol, insufficient calories and carbs, polyunsaturated fat, overtraining, chronic stress, etc.

Easy ways to boost thyroid function is to lower stress by taking a break from stressful situations (e.g. going for a walk, taking time to relax etc.), boosting dopamine (A) and GABA, avoiding gut-irritating foods, getting lots of sunlight, consuming all your vitamins and minerals.

A few diet tips for promoting thyroid function is to eat easily digestible foods, consume calcium-rich foods, consume gelatin via bone broth or supplement (glycine is highly anti-inflammatory and lowers cortisol), eat more carbs than protein, keep PUFA intake as low as possible and try to avoid empty calories (as they use up the body’s nutrients to be processed but don’t provide the body with any nutrients of their own).



Cortisol is a significant negative regulator of muscle growth. It decreases thyroid function and thyroid hormone conversion, lowers IGF-1, increases myostatin and proteolysis (muscle breakdown), induces insulin resistance, inhibits steroidogenesis, increases the aromatase and inhibits muscle protein synthesis.

Cortisol is elevated when thyroid hormones are reduced as well as during inflammation, stress, etc.

Trenbolone, which is one of the most potent anabolic steroids, is a very potent inhibitor of the cortisol receptor. Actually, cortisol receptors are several fold higher in the muscle compared to androgen receptors, thus blocking the cortisol receptor or lowering cortisol levels have a very anabolic effect on the muscle.

Things that increase cortisol is low blood sugar, overexertion, training past fatigue and failure, long distance running, too much HIIT, low carb diet, inflammation, polyunsaturated fat, etc.

Things you can do to keep cortisol in check is to eat a low polyunsaturated diet (PUFAs cause inflammation and I personally found my DOMS are significantly less and my cortisol is much lower when my PUFA intake is low), eat lots of carbs, avoid long workouts, use supplements that lower cortisol, such as glycine, taurine, ornithine, PS, vit D, magnesium, etc.

More on lowering cortisol here


Follistatin & Myostatin

As mentioned above, myostatin reduces anabolism and increases fat mass, whereas follistatin reduces myostatin, boosts muscle growth and lowers fat mass. Fertilized eggs are a great source of follistatin; that’s one reason Vince Gironda advised to eat 2 dozen raw eggs daily.

A few things that decrease myostatin and increase follistatin are:

Endotoxins, inflammation, cortisol, etc, increase myostatin and lowers follistatin.

So the point I’m trying to make is that anything that slows the metabolism, inhibits thyroid function and increases cortisol will negatively affect muscle growth.



Growth hormone actually increases myostatin gene expression, but IGF-1 overrides myostatin. So you don’t want elevated GH, but elevated IGF-1. However, boosting GH to increase IGF-1 isn’t a good idea, in my opinion, and IGF-1 won’t necessarily increase due to higher levels of GH.

IGF-1 significantly increases muscle growth as it stimulates satellite cells, increases glucose and amino transport into the muscles, lowers inflammation, etc.

IGF binding protein 3 (IGFBP-3) prolongs the circulation and biological action of IGF-1, which stimulates muscle hypertrophy. IGFBP-3 and IGF-1 are significantly elevated post workout and are observed to stimulate protein synthesis and subsequently muscle hypertrophy. In fact, IGFBP-3 has been shown to have a significant and direct effect on muscle cell growth, even without the presence of IGF-1.

We want both IGF-1 and IGFBP-3 elevated (balanced) because a low IGF-I:IGFBP-3 ratio is associated with increased waist-to-hip ratio, but a high IGF-1:IGFBP-3 ratio is associated with baldness, cancer and other diseases.

Things that increase IGF-1 are DHEA are vitamin D, vit A, protein, milk, calcium, magnesium, zinc, exercise, egg yolks, potassium, taurine, etc.

Things that increase IGFBP-3 is magnesium, vitamin A, vit B6, zinc, copper, HIIT, etc.

Things that decrease IGF-1 is inflammation, cortisol, intermittent fasting, etc.

Things that decrease IGFBP-3 is estrogen, inflammation, overtraining (increase cortisol to testosterone ratio), endotoxins, etc.



So to take it all together. Thyroid function is really crucial for muscle growth. To further potentiate hypertrophy and strength gains lowering cortisol and boosting follistatin and IGF-1 would be most important. Androgens are also very important, but increasing the number of androgen receptors as well as their sensitivity is more important. Read here on how to boost testosterone, here for DHT and here on how to boost androgen receptors.

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2 Replies to “Most important hormones for muscle growth and tips on how to improve them”

  1. Would the product YOLKED dried fertilized egg yolk powder actually work for lowering myostatin? It uses a patented fertilized egg yolk Fortetropin…ive seen some studies on it but I’m not sure if its good.

    1. I’m sure, but not sure to what extent have how that will impact long-term gains. I think it’s worth a try.

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