Sermorelin: The Brain's Growth Signal, Cut Down to Size

Deep in your brain, a tiny signal tells your body when to let out growth hormone. It is called GHRH. Scientists knew the brain made it. But they could not pin it down.

Then, in 1982, they found it in a strange place: a tumor in the pancreas. The tumor made so much of the signal that a patient's body overgrew. Sermorelin is a short, lab-made copy of that signal.

What it is

A peptide is a short chain of amino acids. Think of amino acids as beads and a peptide as a short bead bracelet. New to this? Start with what a peptide is.

The tumor's signal was a chain of 44 beads. Soon, scientists made a fun find. The first 29 beads alone could still do the job.

Sermorelin is a lab-made copy of those first 29 beads.

It became a real medicine, called Geref. In 1990, the FDA approved it as a test. It showed whether a person's pituitary could make growth hormone. In 1997, it was approved for some children who grew too slowly because they made too little growth hormone.

What it does in the body

Sermorelin works on the pituitary. That is a pea-sized gland under the brain, where growth hormone is made.

Think of a receptor as a lock on a cell and a peptide as the key. Cells in this gland carry a lock for GHRH. When GHRH turns it, the gland lets out growth hormone.

Sermorelin is a copy of the key. It fits the same lock and turns it.

Growth hormone then tells the body to make IGF-1, a helper hormone.

Here is the clever part. Sermorelin does not replace growth hormone. It asks the gland to let out its own. That way, the body keeps its natural pattern.

It is quick, though. In the blood, half of it is gone in about 6 to 7 minutes.

What scientists have found

In cells: In 1984, scientists tried shorter and shorter copies of GHRH on rat pituitary cells in a dish. The 29-bead version still made the cells let out growth hormone. It was about half as strong as the full chain. Cut down to 19 beads, it stopped working.

In animals: In a 1999 study, young and old rats got the 29-bead chain for two weeks. In old rats, the higher of two amounts helped their locks grab the key as tightly as young rats' locks. Their IGF-1 had dipped with age. It went back to normal.

Young rats reacted differently. The same amount lowered their IGF-1 a little and slowed their growth.

In people: The biggest story is growth. In a 1996 study, 110 children with low growth hormone got sermorelin for up to a year. On average, their growth speed nearly doubled within six months. About three in four had a good response, and they handled it well.

Researchers also asked about aging. Growth hormone and IGF-1 tend to fall as people get older.

In a 1992 study, 10 healthy older men, about 68 on average, got two amounts of sermorelin, two weeks each. At the higher amount, their growth hormone and IGF-1 rose to levels like those of young men. Their blood sugar and blood pressure did not change.

Geref's European label listed a warm, flushed face and pain where the shot went in. These came now and then and most often faded within minutes.

Where it stands

Sermorelin was FDA-approved as Geref. Its maker stopped selling it in 2008, and the approval was withdrawn in 2009 at the maker's request. In 2013, the FDA said it had not been pulled for safety or effectiveness reasons. It is on the World Anti-Doping Agency's banned list.

One big question is still open. Could longer use change the body's makeup in older men? Longer, careful studies would be the exciting next step.

Curious about other growth hormone peptides? See CJC-1295 and ipamorelin.

The bottom line

• Sermorelin is a lab-made copy of the first 29 beads of GHRH, the brain's signal to let out growth hormone.
• It asks the gland to release its own growth hormone. In a study of children with low growth hormone, growth speed nearly doubled in six months.
• Once FDA-approved as Geref, it was withdrawn, but not for safety or effectiveness reasons. What longer use does is the next big question.