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IgAnimal studies only

IGF-1 LR3 protocol

IGF-1 LR3 is a lab-made, longer version of IGF-1 built to slip past the proteins that normally carry IGF-1 in blood. It has been studied in cells and rats. I found no human study.

Not an approved medicine: sold as a lab research reagent (vendor sheets say not for human use)No human study of LR3 foundPlain IGF-1 (mecasermin, Increlex) is approved in the US for children with severe IGF-1 deficiency - a different molecule
ProtocolMixingResultsSide effectsHow it worksSources

The protocol at a glance

No human dose of LR3 exists. The only approved IGF-1 product is a different molecule, mecasermin, which has strict dosing and a serious low blood sugar risk.

ItemAmount
Human dose of IGF-1 LR3Not established
Studied inRats (14-day and 7-day treatments) and cell cultures
Different, approved molecule: mecasermin (Increlex), childrenStart 0.04-0.08 mg per kg twice a day under the skin, up to 0.12 mg per kg per dose, with a meal or snack

Rat work: Ballard 1993 (PMID 7683526) and Read 1992 (PMID 1613443). The mecasermin row is the US Increlex label and is shown only so it is not confused with LR3. Do not copy it across.

Community reports

Community reports commonly describe 40-80 mcg a day.

What people say they do, collected from community discussions. Not tested in a trial; shown so you can compare it with the evidence above.

Mixing

No mixing table here: this one is used as a capsule, nasal spray or skin product, or has no human amount to calculate from. The general mixing calculator works for any vial.

What the trials found

No human results exist for LR3, so these are lab and rat facts:

about 1000xLower binding of LR3 to IGF binding proteins than normal IGF-1
5-10xMore potent than IGF-1 in cultured muscle cells
6xMore potent than IGF-1 for growth in rats over 14 days
0Human studies of LR3 found

Effects of interactions between IGFBPs and IGFs on the plasma clearance and in vivo biological activities of IGFs and IGF analogs, Growth Regul 1993 (PMID 7683526). LR3 also cleared from blood faster than IGF-1 in rats.

Side effects

  • Effects in people are unknown for LR3.
  • For approved IGF-1 (mecasermin) in children: low blood sugar in 42% of 71 trial participants, enlarged tonsils in 15%; severe low blood sugar with seizures has occurred.
  • The mecasermin label reports cancers in children, more often at doses above the recommended ones or with IGF-1 above the normal range, and forbids use with active cancer.

How it works

IGF-1 receptor, without the carrier proteins

LR3 has one amino acid swapped (Arg for Glu at position 3) and 13 extra at the start (83 in all). It barely binds IGF binding proteins, so more of it is free to act, but it also clears from blood faster.

Sources

  • Effects of interactions between IGFBPs and IGFs ... Growth Regul 1993, PMID 7683526
  • IGF-I and N-terminal modified analogues induce gut growth in dexamethasone-treated rats, J Endocrinol 1992, PMID 1613443
  • GenScript product sheet, LR3-IGF-I human (structure; research use only)
  • INCRELEX (mecasermin) US prescribing information, DailyMed setid d5b2b0e1-c523-468d-9a0b-4ae4e4a8dbce