What Is Human Growth Hormone (HGH)?
Human growth hormone—or HGH—is one of the most important hormones in your body. Despite its name, it’s not just about growing taller. HGH regulates everything from how your body builds muscle and burns fat to how your skin heals and your immune system functions. Understanding what HGH does and how it changes with age is the foundation for making informed decisions about your health.
HGH at a Glance
- Produced by: Pituitary gland (base of the brain)
- Key roles: Growth, cell repair, metabolism, immune function, body composition
- Measured via: IGF-1 blood test (more reliable than direct HGH testing)
- Decline begins: After age 30 — approximately 10% per decade
- Treatable: Yes — prescription HGH therapy can restore levels when deficient
This comprehensive guide covers the science of HGH in language anyone can understand, so you’ll know whether this hormone might matter for your health.
What Does Human Growth Hormone Do?
Human growth hormone is produced by your pituitary gland—a small gland at the base of your brain—and it affects virtually every cell in your body. Here’s what it actually does:
Growth and Cell Regeneration
HGH is most famous for promoting growth in children and adolescents. It stimulates the growth plates in bones, increases muscle development, and promotes the lengthening of long bones. This is why children with HGH deficiency are shorter, and why HGH replacement therapy in kids helps them reach normal height.
But HGH’s role doesn’t stop once you finish growing. Throughout your life, HGH drives cell regeneration and renewal. It stimulates cells to divide and grow, promoting:
- Hair growth and thickness
- Skin health, elasticity, and healing
- Fingernail and toenail growth
- Tissue repair after injury
- Muscle tissue development and maintenance
Metabolism and Body Composition
HGH profoundly affects how your body uses energy. It increases your metabolic rate and promotes fat breakdown while preserving muscle mass. Specifically, HGH:
- Increases lipolysis—the breakdown of stored fat for energy
- Reduces fat storage and promotes leanness
- Increases protein synthesis, building and maintaining muscle
- Improves insulin sensitivity and glucose metabolism
- Helps you maintain a healthy body composition even as you age
This is why growth hormone deficiency often leads to weight gain, especially around the midsection, and why HGH therapy can help people lose stubborn fat deposits.
Immune System Support
HGH strengthens your immune system by:
- Promoting thymus gland function (the organ that produces immune cells)
- Increasing production and activity of T-cells and other white blood cells
- Improving wound healing and resistance to infection
- Supporting inflammatory response and recovery from illness
People with low HGH often report getting sick more frequently and recovering more slowly. Adequate HGH helps you stay resilient.
How Is HGH Produced?
Your pituitary gland—a pea-sized structure hanging from the base of your brain—produces human growth hormone. But the pituitary doesn’t work independently. It receives signals from the hypothalamus (another brain structure) through a hormone called GHRH (growth hormone-releasing hormone), which tells the pituitary: “Make more growth hormone.”
Another hormone, somatostatin, sends the opposite signal: “Stop making growth hormone.” These two hormones balance each other, creating a finely tuned system.
Two things have the biggest natural impact on your HGH production: sleep and exercise. Most HGH is released during deep sleep (first few hours after falling asleep), and intense physical activity—especially resistance training and HIIT—triggers additional HGH release. Poor sleep and a sedentary lifestyle can significantly suppress your natural HGH output.
What Are Normal HGH Levels?
HGH levels are measured in nanograms per milliliter (ng/mL). However, HGH is tricky to measure because it’s released in pulses throughout the day, not continuously. A single blood test might catch a peak or a valley and give an inaccurate picture.
The IGF-1 marker: Instead of measuring HGH directly, doctors typically measure IGF-1 (insulin-like growth factor 1), a hormone produced by the liver in response to HGH. IGF-1 levels are more stable throughout the day and provide a better picture of your average HGH status.
Normal IGF-1 Ranges by Age
| Age Range | Men (ng/mL) | Women (ng/mL) |
|---|---|---|
| 20–30 | 180–780 | 180–580 |
| 31–40 | 120–480 | 130–440 |
| 41–50 | 100–380 | 100–360 |
| 51–60 | 90–310 | 90–290 |
| 61–70 | 70–250 | 70–230 |
| 71+ | 50–190 | 50–180 |
Lower values suggest growth hormone deficiency. Higher values (though rare in adults) can indicate pituitary tumors or other problems. Your doctor interprets results in context with your symptoms and overall health.
How HGH Changes with Age
HGH production peaks during childhood and adolescence—when growth is rapid—and remains high through your 20s. Then comes the decline.
By age 60, most people have HGH levels only 25–50% of what they had in their 20s. This decline accelerates with poor sleep quality, physical inactivity, increased body fat, chronic stress, and poor nutrition.
What Happens When HGH Is Too Low?
Growth hormone deficiency in adults can be congenital (present from birth) or acquired (developing over time due to pituitary disease, radiation, or head injury). Here are the most common symptoms and how they typically present:
| Symptom | What You May Experience |
|---|---|
| Fatigue and low energy | Feeling tired even after adequate sleep; afternoon crashes |
| Reduced muscle mass | Muscles feel weak; losing tone despite regular exercise |
| Increased body fat | Stubborn weight gain, especially around the abdomen and flanks |
| Thin, dry skin | Loss of elasticity; more wrinkles than expected for your age |
| Reduced sexual function | Lower libido, erectile dysfunction in men |
| Mood and cognitive changes | Depression, anxiety, brain fog, poor memory and concentration |
| Weak bones | Increased osteoporosis and fracture risk, especially in women |
| Poor immune function | Getting sick more often; wounds heal slowly |
| Cardiovascular issues | Increased cholesterol, higher heart disease risk |
For more detailed information, see our guide on low HGH symptoms.
HGH vs. Testosterone
HGH and testosterone are often mentioned together, and people sometimes confuse them. While both are critical hormones that decline with age, they serve different roles in the body:
| Feature | HGH | Testosterone |
|---|---|---|
| Produced by | Pituitary gland | Testes (men) / Ovaries (women) |
| Primary role | Growth, cell repair, metabolism | Sexual development, muscle, bone health |
| Affects | Every cell in the body | Primarily reproductive and musculoskeletal |
| Decline begins | After age 30 | After age 30 (more gradual) |
| Rate of decline | ~10% per decade | ~1–2% per year |
| How it’s measured | IGF-1 blood test | Total and free testosterone blood test |
| Replacement method | Daily subcutaneous injections | Injections, gels, patches, pellets |
| Combined therapy | Often prescribed together — they work synergistically for optimal results | |
Many men benefit from both testosterone and HGH replacement therapy, as they work synergistically. Similarly, women may benefit from HGH along with estrogen and progesterone. Your doctor can assess whether you need one, both, or neither.
When Should You Talk to a Doctor?
If you’re experiencing symptoms consistent with low HGH—persistent fatigue, muscle loss, weight gain, or skin changes despite healthy habits—talk to your doctor about testing. A simple blood test measuring IGF-1 can determine whether HGH deficiency is contributing to your symptoms.
You don’t need to accept age-related decline as inevitable. If you have low growth hormone and symptoms, treatment is available and can transform how you feel and look.
FAQs
Is HGH the same as steroids?
No. HGH (human growth hormone) is a naturally produced hormone that your pituitary gland makes. Anabolic steroids are synthetic versions of testosterone. While both can build muscle, they work differently. HGH is more about overall vitality, metabolism, and tissue repair, while steroids are primarily about muscle and sexual development. Medical HGH therapy is legal with a prescription; anabolic steroids without a prescription are not.
At what age does HGH start to decline?
HGH production peaks in your teens and 20s. It begins declining after age 30, dropping about 10% per decade. By age 60, you have roughly 25–50% of the HGH you had at age 20. This decline is gradual but accelerates with poor lifestyle habits (lack of sleep, inactivity, stress, obesity).
Can you feel when your HGH is low?
Yes, many people notice symptoms of low HGH: persistent fatigue despite good sleep, difficulty building or maintaining muscle despite exercise, stubborn weight gain, thinning skin, reduced energy, and poor mood. However, these symptoms can also be caused by other conditions (thyroid disease, depression, poor sleep), so blood work is necessary for a definitive diagnosis.
What is the difference between HGH and IGF-1?
HGH (human growth hormone) is produced by the pituitary gland. When it circulates in your blood, it stimulates the liver to produce IGF-1 (insulin-like growth factor 1). IGF-1 is actually what does much of the growth-promoting work in your body. Doctors measure IGF-1 levels to assess HGH status because IGF-1 is more stable and accurate than measuring HGH itself, which fluctuates throughout the day.
Is HGH only important for children?
Absolutely not. While HGH is crucial for childhood growth, it remains important throughout life for metabolism, muscle and bone health, immune function, and healthy aging. Many adults benefit from HGH therapy to combat age-related decline and restore vitality.
Does HGH affect aging?
Yes, significantly. HGH levels declining with age contribute to many signs of aging: loss of muscle, weight gain, thin skin, reduced energy, weaker bones, and increased disease susceptibility. Maintaining healthy HGH levels through sleep, exercise, and (if needed) replacement therapy can help you age more slowly and maintain vitality.
Medical Disclaimer: The information on this page is for educational purposes only and is not intended as medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before starting, stopping, or changing any hormone therapy or medication. Individual results vary, and treatment decisions should be made between you and your doctor based on your specific medical history and needs.
National HRT Staff
Please note that the information provided in this article is for informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified healthcare provider with any questions you may have regarding a medical condition or treatment.