Growth Hormone Releasing
Peptide-6

The Discovery

Small Bodies, Big Struggles — The World Before Growth Peptides

When children stopped growing, doctors had almost nothing to offer.

In the 1970s and early 1980s, growth hormone was one of medicine's most precious substances. The only source was human pituitary glands — tiny organs removed from dead bodies. Getting enough to treat just one child took glands from hundreds of donors.

Children with growth problems waited months or years for treatment. Many never got it at all. The supply was so limited that doctors had to choose which kids were "short enough" to deserve the medicine. Families were desperate.

Meanwhile, the science of growth hormone was stuck. Doctors knew the brain's pituitary gland made growth hormone. They knew another brain signal called GHRH told the pituitary when to release it. But something didn't add up. The math was wrong. GHRH alone couldn't explain all the growth hormone the body made.

Scientists suspected there was a second signal — a missing piece of the puzzle. But no one could find it. The search would take decades, and it would start in the most unlikely place: a lab studying painkillers.

The Breakthrough

The Painkiller Accident — How a Wrong Turn Led to a New Science

Cyril Bowers wasn't looking for growth hormone. He found it anyway.

In 1977, Dr. Cyril Bowers was working at Tulane University in New Orleans. He was studying enkephalins — the body's natural painkillers. His team made small tweaks to these painkiller molecules, testing how each change affected their behavior.

Then something unexpected happened. Some of the tweaked molecules made pituitary cells pump out growth hormone. But here was the strange part: they had zero painkiller effects. Bowers had accidentally created molecules that spoke a completely different language to the body.

Most scientists would have filed this away as a curiosity. Bowers didn't. He became obsessed. He brought in Frank Momany, a chemist who used early computers to predict how molecules would fold and fit together. Over the next seven years, they built and tested hundreds of tiny peptides.

In 1984, they published their masterpiece: GHRP-6. Just six amino acids long, it was one of the smallest molecules ever shown to trigger a powerful burst of growth hormone. It worked in test tubes. It worked in chickens, rats, monkeys, lambs, and calves. And it worked through a completely unknown route — not the same path as GHRH.

Bowers made a bold claim: GHRP-6 proves there must be a natural hormone we haven't found yet. Many colleagues rolled their eyes.

The Trials

From Test Tubes to People — Proving GHRP-6 Worked in Humans

The peptide passed every test. But the biggest discovery was still hiding.

Through the late 1980s and 1990s, research teams around the world began testing GHRP-6 in humans. The results were striking. A single injection could boost growth hormone levels several times over within minutes.

But scientists noticed something else. Patients who received GHRP-6 got hungry. Very hungry. The peptide wasn't just talking to the pituitary gland — it was sending signals to parts of the brain that control appetite. It also raised levels of cortisol, the stress hormone, and prolactin.

In 1996, a team finally found the sensor that GHRP-6 was activating — a protein on cell surfaces called the growth hormone secretagogue receptor, or GHS-R. They cloned it and mapped it. But this created an even bigger mystery. The receptor was found not just in the brain, but in the heart, the gut, the immune system, and many other organs.

Why would the body have a sensor for a man-made peptide? It wouldn't — unless the body made its own version. Bowers had been saying this for years. Now the scientific world was finally listening.

The Crisis

The Peptide That Couldn't Get Approved

GHRP-6 changed science forever — but it never made it to the pharmacy shelf.

Despite years of promising research, GHRP-6 ran into walls. The side effects were messy. Every injection triggered a spike in cortisol and prolactin — hormones you don't want elevated over time. The intense hunger it caused made it impractical for many patients.

Drug companies were interested in the concept, but not in GHRP-6 itself. They wanted something cleaner — fewer side effects, maybe a pill instead of an injection. Pharmaceutical giant Merck developed MK-677, an oral compound that hit the same receptor. Other companies made their own versions. GHRP-6 became the starting point everyone built from, but no one wanted to sell.

Then came the black market. As word spread through bodybuilding and anti-aging communities, underground labs began making GHRP-6 for sale online. Quality was wildly inconsistent. Some batches were contaminated. Others were fake. The peptide that Bowers had carefully designed in a university lab was now being cooked up in unregulated facilities around the world.

Researchers watched with frustration. Cuban scientists led by Jorge Berlanga-Acosta were discovering that GHRP-6 could protect hearts during heart attacks, help wounds heal faster, and shield organs from damage. But without FDA approval and without a pharmaceutical company backing it, these discoveries stayed trapped in the pages of research journals.

The Legacy

The Grandfather of Ghrelin — A Peptide That Changed Everything

GHRP-6 never became a drug. But the science it unlocked changed medicine forever.

In December 1999, something remarkable happened in Osaka, Japan. Dr. Masayasu Kojima and Dr. Kenji Kangawa were hunting for the body's natural version of GHRP-6 — the "real key" for the receptor Bowers' "fake key" had been turning. They found it in the last place anyone expected: the stomach.

They named it ghrelin, from the Proto-Indo-European word for "grow." It was a 28-amino-acid hormone that did everything GHRP-6 did — triggered growth hormone, made you hungry, protected the heart — but it was the real thing. The body's own molecule. GHRP-6 had been mimicking it all along.

The discovery of ghrelin opened a flood of new science. Today, thousands of studies explore how ghrelin affects hunger, obesity, metabolism, mood, sleep, and aging. Drugs like MK-677 that target the ghrelin receptor are in clinical trials for muscle wasting and growth hormone deficiency.

And GHRP-6 itself? Cuban researchers continue to explore its wound-healing and organ-protective powers. Early human safety trials have been completed in Havana. The peptide that started as a lab accident in New Orleans may yet find its place in medicine — not as a growth hormone booster, but as a protector of damaged tissue.

Cyril Bowers spent over 40 years at Tulane, watching the field he created grow beyond anything he imagined. The tiny six-amino-acid chain he built in the 1980s didn't just change how we think about growth. It revealed an entire hidden communication system between the stomach and the brain that no one knew existed.