Human Growth Hormone Explained: Everything You Need to Know

Human Growth Hormone Explained: Everything You Need to Know


This peptide hormone, also known as somatotropin, human growth hormone or HGH, is a physiologically active hormone that has a significant role in multiple processes of the human body.

Growth hormone synthesis, production and regulation occurs in the hypothalamus-pituitary axis. These two glands, located in the brain, are responsible for a wide variety of hormone regulation that includes thyroid function, reproductive hormones such as estrogen and testosterone, adrenaline, dopamine, and others in addition to growth hormone. The regulatory process is somewhat complex and has an entire medical specialty dedicated to it known as endocrinology, so I won’t dive any deeper into that discussion but I would encourage you to look it up if you want to know more.


This is an anabolic hormone; in other words it ‘promotes growth’. While this includes skeletal muscle, it’s certainly not limited to it. It’s worth noting that it is not androgenic, as opposed to testosterone, meaning it doesn’t promote male sex characteristics such as facial hair and deeper voice.

The most prominent effect of this hormone is that it promotes bone growth and is the primary hormone responsible for growing to an adult size. In children, it’s largely responsible for determining height, and is modulated by several mechanisms. Secretion peaks during puberty, where the most bone growth occurs, and then declines with age (like most hormones). Along with bone growth, it promotes bone mineralization and calcium retention.

Other functions include:

  • Skeletal muscle proteins synthesis, specifically sarcomere hypertrophy
  • Increase in lean body mass
  • Fat breakdown (lipolysis)
  • Protein synthesis elsewhere (not just muscle)
  • Decrease cellular uptake of glucose
  • Increased glucose synthesis (gluconeogenesis)
  • Release of insulin-like growth factor 1 (will discuss separately)
  • Growth of other organs
  • Pancreas regulation
  • Immune system stimulation
  • Promotes thyroid activity

Too much growth hormone naturally?

There is such a thing as too much from natural sources, not supplementing, and this leads to one of two diseases.

In children who secrete too much growth hormone, often from a pituitary tumor, you get the disease gigantism; think Andre the Giant. The person is excessively tall, often over 7 feet because their growth plates have not yet fused.

If you develop a problem with too much growth hormone as an adult, you get something called acromegaly. The difference is your growth plates are fused so you will not be excessively tall. Instead you have a constellation of symptoms which includes a prominent jaw, large hands, deep voice and a bunch of other symptoms.

Too little growth hormone?

There are a spectrum of diseases that can affect the hypothalamic-pituitary axis that regulates growth hormone secretion. Deficiency can occur as a child (congenital) or as an adult, often secondary to something like a stroke or cancer. There is an FDA approved growth hormone therapy available for these patients.

GH Supplementation and Athletic Performance?

Before I discuss this topic, I want to make it clear that this off label use is illegal and I am not advocating for it. I’m just presenting the limited information available.

There is limited and mixed evidence that supplementing growth hormone will improve athletic performance. It appears that GH does have an anabolic advantage at the molecular level, but it’s not clear that this helps with strength, power or performance.

One double blinded study found no increase on power output or oxygen consumption. Another study did show an increase in IGF-1 but again without the corresponding improvement in strength or performance. Another study found that supplementation improved skeletal muscle synthesis no better than a placebo.

One possible benefit is the buildup of connective tissue, speeding recovery from injury, without any subsequent change in muscle mass or strength. This is theoretical, not evidence based, but widely held to be true in the sports world.

Side effects from supplementing

  • Arthralgia
  • Arthritis
  • Enlarged heart (cardiomegaly)
  • Muscle weakness (myasthenia)
  • High cholesterol (hyperlipidemia)
  • Impaired glucose regulation and increased risk of type I diabetes
  • Impotence
  • Increased fatigue
  • Possible increased cancer risk

Because your body regulates the hormone uses a negative feedback loop, long term supplementation can wreak havoc on your bodies ability to naturally produce growth hormone. In other words, you could stop producing it altogether. This is similar to what happens with long term testosterone supplementation.

Should you supplement?

If you haven’t figured it out, the simple answer is no and it’s illegal, in the US at least. Supplementation should only be done under the supervision of a physician.

The more thoughtful answer is that there is limited and mixed data that it even helps at all. There are no slam dunk studies stating that GH will boost your athletic performance. Rather, the dogma in the sports world exists primarily because of what we know it does naturally and how much supplementing helps out folks who have a growth hormone deficiency.

Furthermore, there are many profound side effects including up to hindering the ability of your body to naturally produce the hormone at all.

Promotes Secretion Naturally?

  • Exercise: well known to allow levels to rise unchecked immediately after exercise
    • This is certainly true of resistance training
    • In endurance training, some studies found long term training can reduce GH
  • Healthy sleep
  • Other
    • Stress
    • Starvation
    • Puberty (as I mentioned)
    • Low blood sugar (hypoglycemia)
    • Other hormones (ie growth hormone releasing hormone)
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