MGF

Key points

• MGF is a splice variant of IGF-1, a growth factor the body makes, produced locally in muscle after stress or damage.
• It is thought to help activate the muscle stem cells involved in repair.
• Most of the research is preclinical, and human evidence as an injected product is very limited.
• It has no UK marketing authorisation, and growth factors are prohibited in sport.

Quick facts

What it is

Mechano growth factor, a local IGF-1 variant

Marketed for

Muscle repair and growth

UK status

Not a licensed medicine; sold for research use

Human evidence

Very limited; mostly laboratory studies

In sport

On the WADA Prohibited List

How it works

When muscle is stretched or damaged, it produces this local form of IGF-1, which is thought to switch on satellite cells, the muscle's own stem cells, to start repair. Injecting a synthetic version is meant to copy that signal. Whether it does so usefully in people is not established.

What the evidence shows

The evidence is mostly from cell and animal studies on muscle repair. There are no controlled human trials showing that injected MGF safely builds or repairs muscle, and no settled dose.

What it does not settle

• There are no controlled human trials of benefit.
• Long term safety is unknown, and products are not quality assessed.
• As a growth factor, there is a theoretical concern about encouraging unwanted cell growth.

Side effects

Less common but serious

• As a growth factor, there is a theoretical concern about cancer, and injecting a product of unknown quality carries real risks.
• Because there is no licensed product, the dose, purity and contents of material bought online cannot be verified.

Report any suspected side effect through the MHRA Yellow Card scheme.

UK legal status and access

MGF has no UK marketing authorisation, so it is not a licensed medicine and is not offered by registered clinics or pharmacies. It is sold online labelled for research use.

Common questions