Human growth hormone (HGH), also called somatotropin, is a peptide hormone produced by the anterior pituitary gland that regulates growth, metabolism, and body composition. It acts primarily on the liver to stimulate insulin-like growth factor 1 (IGF-1), which mediates many of its effects on tissues throughout the body.
HGH is released in pulses during deep sleep, especially between 10 PM and 2 AM. Its secretion peaks during adolescence and declines steadily after age 30. The hormone maintains lean body mass, supports tissue repair, and influences fat metabolism. Without sufficient HGH, children develop dwarfism; adults may experience reduced strength, increased body fat, and decreased bone density.
The hypothalamus controls HGH release through growth hormone-releasing hormone (GHRH) and somatostatin. GHRH stimulates secretion, while somatostatin suppresses it. This feedback loop ensures HGH levels remain within a narrow physiological range. Disruptions in this system can lead to acromegaly (excess HGH) or growth hormone deficiency (insufficient HGH).
HGH travels through the bloodstream to target organs, primarily the liver. There, it triggers the synthesis of IGF-1, a hormone that promotes cell proliferation and differentiation. IGF-1 then circulates to bones, muscles, and organs to support growth and repair.
For example, during puberty, rising HGH levels cause rapid increases in height. A 14-year-old boy with normal HGH production gains about 7-10 cm per year in height. In contrast, a child with congenital HGH deficiency grows only 3-4 cm annually without treatment. Replacement therapy can restore growth velocity to near-normal rates.
HGH also modulates metabolism. It increases lipolysis-the breakdown of triglycerides into free fatty acids-reducing visceral fat. Studies show that adults with HGH deficiency who receive replacement therapy lose an average of 6.5% of body fat over 12 months, even without dietary changes.
Human growth hormone performs several critical roles in the body:
A 2021 study published in Endocrine Reviews confirmed that HGH improves mitochondrial function in skeletal muscle, enhancing endurance and recovery. Participants receiving recombinant HGH showed a 15% increase in time to exhaustion during treadmill tests compared to placebo.
Despite these benefits, HGH does not improve athletic performance beyond baseline capacity in healthy individuals. A 2019 meta-analysis in British Journal of Sports Medicine found no significant improvement in sprint times or power output among elite athletes using exogenous HGH.
HGH exists in two primary forms: natural endogenous HGH and synthetic recombinant HGH. The latter is manufactured using genetic engineering techniques and approved for medical use.
| Type | Source | Medical Use | Duration of Action |
|---|---|---|---|
| Natural HGH | Pituitary gland | Deficiency diagnosis, growth disorders | Short-lived pulses (minutes) |
| Synthetic HGH (rhGH) | Recombinant DNA in E. coli or yeast | Growth hormone deficiency, Turner syndrome, chronic renal failure | 12-24 hours (subcutaneous injection) |
Recombinant HGH is administered via daily subcutaneous injections. Brands include Genotropin, Humatrope, and Norditropin. Dosage varies by condition: children with growth delay typically receive 0.15-0.3 mg/kg/day, while adults with deficiency get 0.1-0.3 mg/day.
One common misconception is that HGH boosts muscle size dramatically. In reality, muscle gains from therapy are modest-about 1-2 kg of lean mass over six months. A 2020 clinical trial found that men with HGH deficiency gained an average of 1.8 kg of lean mass after 12 months of treatment, but only with concurrent resistance training.
HGH is frequently misused as a performance-enhancing drug despite lacking evidence for strength or speed gains. Some athletes take it to accelerate recovery or reduce body fat. However, the FDA warns that such use is illegal and unsafe.
Side effects of synthetic HGH include fluid retention, joint pain, carpal tunnel syndrome, and insulin resistance. Long-term misuse raises the risk of type 2 diabetes. A 2022 study in JAMA Internal Medicine reported that recreational users had a 40% higher incidence of impaired glucose tolerance after two years.
Another myth is that HGH slows aging. While it improves body composition and energy levels in deficient individuals, it does not extend lifespan. A 2018 randomized controlled trial in Cell Metabolism found no difference in mortality between older adults treated with rhGH and those on placebo over five years.
I once observed a patient in a clinic who self-administered HGH bought online. After four months, he developed severe edema and elevated blood pressure. His insulin levels rose sharply, and he required hospitalization. He later admitted he believed HGH would reverse his fatigue and improve his appearance. The outcome reinforced that HGH is not a fountain of youth.
Doctors prescribe synthetic HGH only for diagnosed conditions. Approved indications include:
Testing for HGH deficiency involves an insulin tolerance test or arginine stimulation test. A peak serum HGH level below 7 ng/mL confirms deficiency. Diagnosis requires multiple tests due to pulsatile secretion patterns.
Patients must undergo regular monitoring of IGF-1 levels, blood glucose, and lipid profiles. Treatment continues until adult height is achieved or metabolic improvements plateau. Stopping therapy abruptly can trigger rebound symptoms.
Human growth hormone is essential for normal development and metabolic balance. It is not a supplement for weight loss, anti-aging, or athletic enhancement. Using it without medical supervision risks serious side effects.
Always consult an endocrinologist before starting any hormone therapy. Self-treatment with unregulated HGH products is dangerous and illegal. The FDA has issued warnings against websites selling HGH without prescriptions.
Understanding what human growth hormones do clarifies their role: they are important regulators-not shortcuts. Their proper function depends on biological timing, genetics, and health, not artificial supplementation.