IGF-1

Where it comes from

Made in

The liver, under growth hormone; also made locally in bone, muscle and brain

Sent out by

Growth hormone and nutrition raise it; fasting, illness and liver disease lower it. Nearly all of it travels bound to IGFBP-3

Acts on

• Growth plates
• Muscle
• Bone
• Nearly every tissue

What it does

• Drives childhood growth and adult tissue upkeep
• Builds muscle and bone protein
• Feeds back to shut off growth hormone

In medicine

• Measured to diagnose acromegaly and growth hormone deficiency: a stable readout where growth hormone itself comes in pulses
• Mecasermin, recombinant IGF-1, is approved (2005) for children with severe primary IGF-1 deficiency, a rare condition ¹
• High-normal IGF-1 is linked with some cancers and low IGF-1 with heart disease in cohorts; what to make of it is still debated

Beyond the body’s own use

• IGF-1 LR3 and DES(1-3) IGF-1, laboratory versions altered to escape the binding proteins, are used in doping. Neither is approved for anything, both are banned in sport at all times ², both can cause hypoglycaemia, and preparations obtained outside the approved supply are not reviewed for safety, effectiveness or quality
• Low IGF-1 runs in some long-lived families and in Laron syndrome, where cancer has been almost absent among the patients followed so far ³. That is the basis of the claim that lowering IGF-1 extends life, and no trial in people has tested it
• Growth hormone injections raise IGF-1, which is why the two are misused together and why a raised IGF-1 is what anti-doping tests look for ²