IGF-1 LR3 quick reference
What is IGF-1 LR3?
IGF-1 with changes that stop binding proteins from holding it.
People use it for muscle fullness and recovery.
No human LR3 study exists; mecasermin is a different approved drug.
How IGF-1 LR3 works
Switches on growth and glucose-uptake signals.
About 1000x weaker binding than IGF-1.
6x the growth effect of IGF-1 over 14 days.
Leaves rat blood sooner than IGF-1.
What IGF-1 LR3 is studied for
14 days: 6x more potent than IGF-1 for growth.
5-10x more potent than IGF-1 in cultured muscle cells.
Gut weight rose in dexamethasone-treated rats in 7 days.
Daily injections still beat IGF-1 in rats, but less than a pump.
Barely matched IGF-1 at reversing muscle loss in rats.
IGF-1 LR3 dosing protocol
| Item | Amount |
|---|---|
| Human dose of IGF-1 LR3 | Not established |
| Studied in | Rats (14-day and 7-day treatments) and cell cultures |
| Different, approved molecule: mecasermin (Increlex), children | Start 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.
Label and trial amounts come from the sources below. Community amounts are what people report; they have not been tested.
Mixing
Supplier sheets differ: dilute acid or water. Check yours.
What the research found
No human results exist for LR3, so these are lab and rat facts:
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.
IGF-1 LR3 community experience
What users report. Not tested in trials.
Positive reports
- Fuller muscles Some describe a pump and better training response.
- Appetite A few report stronger hunger.
- Recovery Some feel quicker between hard sessions.
Negative & mixed
- Low blood sugar Shakiness or weakness is the main worry.
- Swelling Swelling, numbness and joint aches appear in reports.
- Headache Headache and site irritation also reported.
- Hard to credit Other anabolics and training blur the cause.
IGF-1 LR3 stacking
IGF-1 feedback may blunt GH pulses. Not studied together.
Both lower blood sugar. Severe lows are possible.
Different pathways. Not studied together.
IGF-1 LR3 side effects & safety
Common
- No human LR3 data on side effects.
- Mecasermin: low blood sugar in 42% of 71 trial participants.
- Mecasermin: enlarged tonsils in 15%.
- Swelling, joint aches, headache (community).
Less common
- Mecasermin label: severe lows with seizures.
- Mecasermin label: cancers reported in children.
- Label: raised skull pressure, hip slippage, scoliosis worsening.
- Long-term LR3 risks in people are unknown.
Precautions
- Mecasermin label bars use with cancer or past cancer.
- Mecasermin is dosed within 20 minutes of a meal (low sugar).
- With insulin or glucose-lowering drugs, lows can be severe.
- Not approved; no human LR3 dose exists.
Our verdict on IGF-1 LR3
Strong effects in rats, unknown in people. Low blood sugar and growth risks are the known concerns.
IGF-1 LR3 FAQ
Is IGF-1 LR3 approved?
No. Only mecasermin, a different molecule, is approved (children).
How does LR3 differ from IGF-1?
A swap at position 3 plus an extension reduce binding-protein grip.
Does it last longer in blood?
No. In rats it cleared faster than IGF-1.
Is LR3 safe for people?
Unknown. No human LR3 safety data exist.
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
- Superior potency of infused IGF-I analogues ... maintained when injected, J Endocrinol 1996, PMID 8708565