Yes, human growth hormone (HGH) is officially classified as a performance-enhancing drug. The World Anti-Doping Agency (WADA) and the International Olympic Committee both ban its use in competition, and distributing it for non-medical purposes in the United States is a federal felony carrying up to five years in prison.
But the reality of HGH as a performance enhancer is more nuanced than its reputation suggests. It does change body composition and boost connective tissue repair, yet its effects on raw strength and power are less dramatic than many athletes assume.
Where HGH Sits on the Banned List
WADA places HGH under Section S2 of its Prohibited List, categorized alongside other peptide hormones, growth factors, and related substances. It is banned at all times, both in and out of competition. This means any athlete subject to anti-doping rules cannot use HGH regardless of whether they’re in the off-season or actively competing.
In the U.S., HGH occupies a unique legal space. It is not a controlled substance under the Controlled Substances Act, which means it’s treated differently from anabolic steroids from a scheduling perspective. However, the 1990 Anabolic Steroids Control Act made it a five-year felony to distribute or possess HGH with intent to distribute for any purpose other than treating a recognized medical condition, prescribed by a physician and authorized by the Secretary of Health and Human Services. Legitimate medical uses include adult growth hormone deficiency, muscle wasting from HIV, and short bowel syndrome.
How HGH Changes the Body
HGH works primarily through a secondary hormone. When you inject synthetic growth hormone, your liver responds by producing large amounts of insulin-like growth factor I (IGF-I). This is the real workhorse. IGF-I triggers a signaling chain in cells that ramps up protein production while simultaneously slowing protein breakdown. Growth hormone also stimulates IGF-I production directly inside muscle tissue, and this local production appears to matter more for muscle growth than the amount circulating in your bloodstream. In animal studies, directly infusing growth hormone into a single muscle increased both IGF-I levels and muscle size in that specific muscle.
The fat loss effects are equally well documented. Within one to two hours of exposure, growth hormone begins breaking down stored fat and releasing fatty acids into the bloodstream, with peak fat-burning effects around three to four hours later. It does this by activating an enzyme that breaks apart fat cells and by switching off a protein that normally keeps fat stored. Long-term growth hormone use produces a sustained, gradual reduction in body fat. This combination of increased lean mass and decreased fat mass is what makes HGH so appealing to athletes looking to improve their body composition.
What HGH Actually Does for Performance
Here’s where the science gets interesting, and where HGH’s reputation outpaces the evidence. A study in healthy men over 60 found that three months of growth hormone treatment increased lean body mass by about 3.3 kg (roughly 7 pounds) and muscle mass by a similar amount, with thigh strength improving by about 14%. Those numbers sound impressive, but the researchers noted something important: HGH did not increase the rate at which muscle fibers actually build new contractile protein. In other words, the muscles got bigger but not necessarily through the same mechanism that makes them more powerful.
A separate study in healthy young adults confirmed this pattern. Fourteen days of growth hormone administration dramatically increased collagen production in both tendons and muscles, with tendon collagen gene expression jumping nearly 4-fold and muscle collagen gene expression rising about 2.3-fold. But there was zero effect on myofibrillar protein synthesis, the process that builds the contractile fibers responsible for generating force. The gains in “lean mass” from HGH may partly reflect more connective tissue and water retention rather than pure muscle fiber growth.
This distinction matters. An athlete using HGH might look more muscular and weigh more on a scale, but the improvement in actual explosive power or maximal strength is likely smaller than what anabolic steroids deliver. Where HGH may genuinely shine is in recovery. The massive boost in collagen synthesis holds real potential for repairing damaged tendons and muscle connective tissue after injury, which is likely one reason it remains popular among professional athletes despite the testing risks.
Health Risks of Using HGH
The most significant long-term risk of excess growth hormone is insulin resistance. Growth hormone directly opposes insulin’s effects by flooding the bloodstream with fatty acids, reducing glucose uptake in muscles, and increasing sugar production in the liver. The body compensates by producing more insulin, but over time this compensation fails. Among people with acromegaly (a condition of chronic growth hormone overproduction), more than 50% have impaired glucose metabolism at diagnosis, and 20 to 35% develop diabetes.
The heart is also vulnerable. Excess growth hormone and IGF-I cause structural changes to the heart muscle, a condition called acromegalic cardiomyopathy. When high blood pressure develops alongside it, the damage accelerates. These cardiac changes resemble what happens in diabetic heart disease, creating a compounding risk for anyone using HGH long-term at supraphysiological doses.
Other documented effects of chronic growth hormone excess include sleep apnea, joint pain, fluid retention, and carpal tunnel syndrome. There is also an association with increased cancer risk, since IGF-I is a potent growth signal that doesn’t distinguish between healthy cells and abnormal ones.
How Anti-Doping Agencies Detect It
Testing for HGH has historically been difficult because synthetic growth hormone is chemically identical to the natural version and clears the body quickly. Anti-doping agencies now use two complementary approaches.
The first is the isoform test, which exploits the fact that your pituitary gland naturally releases several slightly different forms of growth hormone. When you inject synthetic HGH, it’s a single pure form, which throws off the normal ratio of isoforms in your blood. This test works best within 24 to 48 hours of injection.
The second is the biomarkers test, which measures two substances that rise when growth hormone levels are elevated: IGF-I and a collagen byproduct called P-III-NP (a fragment released when the body builds new collagen). WADA uses specific immunoassay and mass spectrometry methods to measure these markers. Because IGF-I and P-III-NP stay elevated longer than growth hormone itself, this test has a wider detection window, making it harder for athletes to time their use around testing schedules.