Bodybuilders take human growth hormone (HGH) because it simultaneously builds lean tissue and strips body fat, a combination that anabolic steroids alone don’t achieve as effectively. HGH also strengthens tendons and ligaments, speeds recovery between training sessions, and helps bodybuilders maintain a fuller, harder look while dieting for competition. It has become a staple in competitive bodybuilding since the 1990s, though it carries serious health risks that escalate with the high doses commonly used.
How HGH Builds Muscle
HGH doesn’t act on muscle the way most people assume. Rather than directly forcing muscle fibers to grow the way testosterone does, it works through a middleman. When you inject HGH, it travels to the liver, where it triggers the production of a secondary hormone called IGF-1. IGF-1 is the real workhorse: it activates a signaling chain inside muscle cells that ramps up protein synthesis and, just as importantly, blocks protein breakdown. The net effect is that more protein accumulates in the muscle.
IGF-1 also activates satellite cells, which are dormant precursor cells that sit on the surface of muscle fibers. When a muscle fiber grows beyond a certain size, it needs additional cellular machinery to support itself. Satellite cells fuse into the fiber and donate their nuclei, giving the muscle the capacity to keep growing. This process, called hyperplasia, is one reason bodybuilders believe HGH produces a different quality of muscle growth compared to steroids alone.
Interestingly, research on human tendon and muscle tissue found that HGH strongly stimulates collagen production in the connective tissue surrounding muscle but has little direct effect on the contractile proteins inside the muscle fiber itself. This suggests that much of HGH’s muscle-building reputation actually comes from its indirect effects through IGF-1 and its synergy with other compounds, rather than from HGH acting on muscle cells directly.
The Fat-Burning Effect
Fat loss is arguably the main reason bodybuilders value HGH. Growth hormone is powerfully lipolytic, meaning it forces fat cells to release stored fatty acids into the bloodstream so they can be burned for energy. This effect kicks in about one to two hours after injection and peaks around three to four hours later. HGH accomplishes this by activating an enzyme inside fat cells that breaks apart stored triglycerides, while also blocking fat cells from reabsorbing those released fatty acids. The result is a one-two punch: fat gets released faster and stored back more slowly.
For bodybuilders preparing for competition, this is enormously valuable. Contest prep requires getting to extremely low body fat levels while preserving as much muscle as possible. HGH shifts the body’s fuel preference toward fat, sparing muscle protein. In the fasting state, it actively mobilizes stored fat for energy. Between meals, it works alongside insulin to promote protein retention. This dual action, building tissue while burning fat, is something few other compounds deliver.
The fat loss tends to be especially pronounced in visceral fat, the deep abdominal fat surrounding the organs. Bodybuilders using HGH often report a thinning of the skin and a more “grainy” or vascular appearance as subcutaneous fat decreases.
Faster Recovery and Stronger Connective Tissue
Competitive bodybuilders train with extreme volume and intensity, which places enormous stress on tendons, ligaments, and joints. HGH directly stimulates collagen synthesis in both tendons and skeletal muscle connective tissue. Collagen is the primary structural protein responsible for transmitting force from muscle to bone, and stronger collagen means more resilient joints and a lower risk of tears or ruptures.
A placebo-controlled trial with over 400 patients found that high-dose growth hormone treatment significantly shortened healing time for closed bone fractures. Smaller studies on Achilles tendon ruptures showed improved range of motion and faster recovery when growth factors including IGF-1 were applied. For bodybuilders who are constantly loading heavy weight onto joints already strained by rapid muscle growth, this recovery advantage is a practical reason to include HGH in their protocols.
Why Bodybuilders Stack HGH With Other Compounds
HGH is rarely used alone in competitive bodybuilding. It is almost always combined with anabolic steroids and often with insulin, because each compound amplifies the others through overlapping but distinct pathways.
Anabolic steroids directly increase protein synthesis inside muscle fibers, something HGH does only indirectly through IGF-1. When used together, the steroid drives the contractile muscle proteins to grow while HGH strengthens the surrounding connective tissue and promotes fat loss. Adding IGF-1 on top further enhances the anabolic signal.
Insulin enters the picture because of how it interacts with both glucose and protein metabolism. Bodybuilders typically inject insulin around post-workout meals to drive glucose and amino acids into muscle cells, shutting down protein breakdown while fueling recovery. Insulin also increases the liver’s sensitivity to growth hormone, which means more IGF-1 gets produced per unit of HGH. This creates a synergistic loop: HGH raises IGF-1, insulin makes the liver more responsive to HGH, and all three hormones converge on the same protein-building pathway inside muscle cells.
The Distended “HGH Gut”
One of the most visible side effects in modern bodybuilding is the so-called “bubble gut” or “Palumboism,” where competitors display a dramatically distended abdomen despite having extremely low body fat. This is strongly linked to chronic high-dose HGH use.
The mechanism involves the same growth signals that build muscle. When HGH stimulates IGF-1 production in the liver, that IGF-1 binds to receptors on the lining of the intestines, driving excessive cell proliferation throughout the gut wall. Animal studies on mice engineered to overproduce growth hormone showed a 50 to 100 percent increase in the mass of the intestinal lining, along with significant increases in bowel weight and length. In humans with acromegaly (a condition of natural GH overproduction), the same pattern of broad intestinal cell growth appears.
On top of intestinal growth, prolonged HGH use can cause actual organ enlargement, a condition called organomegaly. The liver, kidneys, and heart can all increase in size. When abdominal organs grow larger and intestinal tissue thickens, the abdomen pushes outward regardless of how lean the bodybuilder is. This is why some competitors can display shredded abdominal muscles stretched over a visibly protruding midsection.
Insulin Resistance and Blood Sugar Problems
HGH has a well-documented diabetogenic effect. By mobilizing so much fat into the bloodstream, it floods the body with free fatty acids. These circulating fatty acids interfere with insulin signaling in both muscle and liver tissue, making cells less responsive to insulin. At the same time, the excess fatty acids reaching the liver promote the production of new glucose, further raising blood sugar levels.
For bodybuilders using supraphysiological doses, this creates a real risk of developing insulin resistance or outright type 2 diabetes. The risk compounds when insulin is added to the stack: bodybuilders use exogenous insulin partly to counteract HGH’s blood sugar effects, but the combination requires precise management. Miscalculating insulin doses can cause dangerously low blood sugar, which is one of the most acute risks in bodybuilding pharmacology.
Other Physical Side Effects
Because HGH stimulates growth in virtually all tissues, not just muscle, chronic use produces changes throughout the body. Bones and cartilage respond to sustained high levels by thickening. The brow ridge becomes more prominent, the jaw grows larger, and the hands and feet widen. Spacing between teeth can increase as the jawbone expands. These changes, characteristic of acromegaly, are irreversible.
Joint pain is another common complaint. While moderate HGH use strengthens connective tissue, excessive levels cause cartilage and bone to grow in ways that alter joint mechanics. Carpal tunnel syndrome, where swelling compresses the nerve running through the wrist, is particularly frequent among HGH users. Water retention, especially in the hands and feet, adds to the discomfort and is one of the earliest noticeable side effects.
Perhaps most concerning is the effect on the heart. The heart is a muscle, and it responds to sustained HGH exposure by growing larger. Unlike the beneficial heart enlargement seen in endurance athletes, HGH-driven cardiac growth tends to thicken the heart wall in ways that can impair its ability to relax and fill with blood, raising the long-term risk of heart failure.
Detection in Drug Testing
HGH has historically been one of the hardest performance-enhancing drugs to detect. Because it is identical in structure to the growth hormone the body produces naturally, standard urine tests cannot distinguish between the two. Detection requires blood testing using specialized kits approved by the World Anti-Doping Agency, which measure the ratio of different growth hormone forms in the blood. Natural GH comes in a mix of molecular variants, while synthetic HGH is a single form. An abnormal ratio flags recent use.
The detection window is narrow, often just 24 to 48 hours after injection, which makes catching users difficult. This short window, combined with the fact that blood testing is more invasive and expensive than urine testing, is a major reason HGH remained virtually undetectable in competitive sports for decades and continues to be widely used.