Growth hormone

PEG-MGF

The 25 percent that sells it came from injecting a gene

7 sections

Top of article
What it actually is
What it is supposed to do
What people take it for
The dose question
How to check you have the right molecule
What people get wrong
What is known about harm

What circulates: 200 to 400 mcg two to three times a week, and daily in the same row
What was studied: No dose in a person, or in a live animal of any species, that I could find
The gap: No published human dose to compare against
How long it lasts: This is the whole selling proposition and the part I could not source. What circulates is about 5 to 7 minutes for the native peptide against 48 to 72 hours once the polymer is attached, and the two figures do not come off the same page. One vendor page prints the 48 to 72 hours. A second prints several hours to days against 5 to 7 minutes, and says on that same page that no human data on how the compound moves through the body exists and that the right dose for any use is unknown. I could not trace either number to a measurement in any species, and the one peer reviewed source I found that treats PEG-MGF as a compound records the half-life as not reported.

What it actually is

PEG-MGF is a lab made chain of 24 amino acids, the small units that proteins are built from. Short chains like this are called peptides, and this one has polyethylene glycol attached, an inert polymer that makes a molecule bigger so the kidney clears it more slowly. Three things get called the same thing here. Insulin like growth factor 1 is the growth signal the liver puts out when growth hormone reaches it, and the mature protein is 70 amino acids. Mechano growth factor is not a second molecule, it is one of the messages that same gene produces. The peptide in the vial is built from the end of what that message spells out, and it is the offcut left when the mature protein is cut away, so it does not contain it. The step people skip is the middle one. The message is real. The peptide made from it is a prediction read off the gene, and a 2010 review in Endocrinology recorded that no such peptide had been isolated from cells, medium, animal tissue or fluid.

What it is supposed to do

The selling story is that this fragment makes the reserve cells that repair muscle divide instead of settling down. Yang and Goldspink reported in 2002 that the fragment made cultured immature muscle cells divide more and mature less, and that it did so through something other than the insulin like growth factor 1 docking point. Twelve years later Fornaro and colleagues, working at two pharmaceutical companies, could not reproduce it: concentrations up to 500 nanograms per millilitre moved nothing in mouse muscle cells, in human muscle cells or in primary mouse muscle stem cells, while the mature growth signal and the full length uncut version both worked in the same hands. Neither of the two versions of the 24 amino acid peptide in circulation switched on the human insulin like growth factor 1 docking point in a dish, though the whole uncut prohormone did. The same 2010 review recorded that as of its writing no docking point of its own had been found for this fragment.

What people take it for

People buy it for muscle growth and for repair after training. The number behind that is a 25 percent increase in muscle fibre size in two weeks, which appears on every sales page I opened, and it came from injecting a gene rather than a peptide. The one live animal study I found that tested muscle repair itself injected the unpegylated peptide into bruised muscle in mice whose immune scavenger cells had been stripped out, and found no protection of muscle fibre regeneration, though scarring fell. The authors read it more softly than that: their title says the regeneration failure caused by removing those cells could be partly ameliorated by the injection.

The dose question

What circulates: 200 to 400 mcg two to three times a week, and daily in the same row
What was studied: No dose in a person, or in a live animal of any species, that I could find; FDA states it has identified no human exposure data on PEG-MGF products by any route

No studied dose to compare

There is nothing to compare against. I found no published study giving PEG-MGF to a person and none giving it to a live animal of any species, and the regulator says the same about the human half. The nearest published figure per kilogram I found belongs to the unpegylated 24 amino acid peptide, injected into a surgical bone defect in 27 rabbits at 28.5 and 57 micrograms per kilogram, where only the higher dose separated from no treatment. Against that dose the circulating amount is 11 to 23 times smaller per kilogram, and it went into bone rather than muscle or fat.

Reported because it is what people use. Nothing here recommends any amount.

How long it lasts

This is the whole selling proposition and the part I could not source. What circulates is about 5 to 7 minutes for the native peptide against 48 to 72 hours once the polymer is attached, and the two figures do not come off the same page. One vendor page prints the 48 to 72 hours. A second prints several hours to days against 5 to 7 minutes, and says on that same page that no human data on how the compound moves through the body exists and that the right dose for any use is unknown. I could not trace either number to a measurement in any species, and the one peer reviewed source I found that treats PEG-MGF as a compound records the half-life as not reported.

Route studied

None that I could find. I found no published study giving PEG-MGF to a person, and none giving it to a live animal of any species. The live animal record belongs to the unpegylated peptide: injected locally into a surgical bone defect in rabbits, into the heart muscle in mice inside implanted polymer rods the peptide seeped out of, and into bruised muscle in mice.

Route used

Injected under the skin or into a muscle after training. That is what circulates, reported as convention and not as a tested schedule.

How to check you have the right molecule

Ask what the certificate of analysis says about the polyethylene glycol, because on the specifications I could reach it says nothing at all. A vendor selling PEG-MGF prints a molecular weight of about 2,867 grams per mole, qualified on the page as the core peptide and varying with the size of the polymer. The free 24 amino acid peptide the gene encodes weighs about 2,868, so the polymer that is the entire reason the product has a different name contributes nothing to the number, and no chain length, chain count or attachment site is given. The formula printed beside it is that peptide with its tail capped as an amide, which is a chemically different molecule one unit lighter. The sequence to hold a report against is YQPPSTNKNTKSQRRKGSTFEERK, and you can check it yourself against UniProt entry P05019. Two anti doping laboratories that opened black market unpegylated material found an altered molecule instead, with the last amino acid missing and one arginine swapped for a histidine.

Walked through on two real certificates in how to read a certificate of analysis.

What people get wrong

The costly mistake is treating a gene experiment as a peptide result. The 25 percent figure comes from Goldspink's own account in Physiology News in 2003 of injecting the gene into muscle in a loop of DNA, so the muscle manufactured the product itself, and his sentence names no species. Injecting a gene and injecting a peptide are different operations, the way installing a boiler and carrying in a bucket of hot water are, and one of them keeps producing. The only source cited for that figure is United States patent 6,221,842 B1, and I searched that patent's full description: no 25 percent, no fibre measurement, no loop of DNA and no mice. The second mixup is a different molecule with a similar name: RO5046013 is a pegylated insulin like growth factor 1 that went into a first in man study in 62 healthy volunteers, and none of its numbers belong to this compound.

What is known about harm

There is no human safety record to report, because I found no study of it in a person. Two things sit around that gap. The same fragment has been studied in cancer biology: Armakolas and colleagues found the matching isoform in prostate cancer biopsies with expression tracking tumour stage, and prostate cells engineered to overexpress the peptide divided more, took on the migratory state that comes before spread, and seeded more tumours in mice. The same Athens laboratory later raised the growth of one oestrogen responsive human breast cancer line, though not a hormone resistant one, by adding the synthetic peptide from outside. Those two papers share authors, so the second is not an independent repeat of the first, and the prostate work is a genetic manipulation rather than an injection. In September 2023 the United States drug regulator put PEG-MGF in the category it reserves for substances it has identified significant safety risks with. It has since come off that list, filed under substances withdrawn by the people who nominated them rather than under substances cleared.

Others in Growth hormone

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