Sermorelin and IGF-1 LR3 are searched against each other by people looking at growth-hormone-related peptides. The comparison is lopsided in a way most pages skip. Sermorelin was an FDA-approved drug for nearly two decades, with a published pivotal trial; IGF-1 LR3 is a laboratory analogue that has never been given to a person in a registered study. They also act at opposite ends of the same chain. This page sets out both records and converts the circulating figures into syringe units.
The full record for each is on sermorelin dosage and IGF-1 LR3 dosage. The same upstream-against-downstream contrast with a longer-acting releaser is on CJC-1295 vs IGF-1 LR3. Sermorelin beside a growth hormone fragment that left IGF-1 unchanged in its trials is on sermorelin compared with AOD-9604.
Side by side
| Sermorelin | IGF-1 LR3 | |
|---|---|---|
| What it is | GHRH(1-29), 29 amino acids; C149H246N44O42S, MW 3,357.9 (PubChem CID 16132413) | IGF-1 with arginine at position 3 and a 13-residue N-terminal extension |
| Where it acts | GHRH receptor in the pituitary → growth hormone → IGF-1 | IGF-1 receptor, directly |
| FDA history | Approved as GEREF (NDA 020443, NDA 019863), discontinued; not withdrawn for safety or effectiveness | Never approved |
| Label served today | None (DailyMed, 2026-11-10) | None; mecasermin is a different molecule |
| Registry records (ClinicalTrials.gov, 2026-11-10) | 42 mention it | 0 |
| Human dosing on record | 30 mcg/kg nightly in children (1996); 1 mcg/kg intravenous in stimulation tests | None |
Upstream and downstream
Sermorelin's effect depends on the body's own system. It releases growth hormone in pulses that the pituitary still regulates, and the IGF-1 that follows is made by the liver within its usual feedback limits. That is the basis on which it was approved: the 1996 multicentre trial gave 30 micrograms per kilogram a day under the skin at bedtime to 110 growth-hormone-deficient children, and mean height velocity rose from 4.1 cm a year at baseline to 8.0 cm a year at six months and 7.2 cm at twelve (Thorner et al., 1996).
IGF-1 LR3 bypasses the pituitary and the liver. Its two changes — arginine at position 3 and an N-terminal extension — reduce binding to the IGF binding proteins that normally hold most circulating IGF-1 inactive, so more of it reaches the receptor. Nothing regulates it but its own clearance, and that clearance has not been measured in people. The record for it is cell work, doping analysis and animal studies, set out on the IGF-1 LR3 page.
The closest approved reference for each
| Compound | Closest approved reference | What the reference states |
|---|---|---|
| Sermorelin | GEREF itself (discontinued) | 30 mcg/kg once daily at bedtime in the pivotal paediatric trial |
| IGF-1 LR3 | Mecasermin (INCRELEX), a different molecule | 0.04–0.08 mg/kg twice daily, maximum 0.12 mg/kg twice daily; 10 mg/mL |
The INCRELEX label prints its own conversion, weight × dose × 1 mL/10 mg × 100 units/mL, so at its concentration one unit is 100 mcg. No IGF-1 LR3 vial carries anything comparable, and the mecasermin figures do not transfer: an analogue built to escape the binding proteins is not interchangeable with native IGF-1 milligram for milligram.
The figures in circulation
| Compound | Figure recorded on this site's dosage page (2026-09-18) | Per week |
|---|---|---|
| Sermorelin | 200–500 mcg under the skin once nightly | 1.4–3.5 mg |
| IGF-1 LR3 | 20–100 mcg a day, 4–6-week cycles | 0.14–0.7 mg |
By mass the weekly sermorelin figure is about five times the IGF-1 LR3 one at either end of the ranges. That compares milligrams only: the two act at different points of the chain, and a microgram of a direct receptor agonist is not equivalent to a microgram of a releaser. Neither range comes from a trial. Scaled to a 70 kg adult, the paediatric 30 mcg/kg regimen would be 2.1 mg a day, four to ten times the circulating sermorelin figure, which shows the circulating figures were not taken from the approved product's trial.
Both in syringe units
Sermorelin is sold in 5 mg and 10 mg vials; IGF-1 LR3 in 0.1 mg and 1 mg vials. On a U-100 syringe, units = amount ÷ concentration × 100.
| Vial and water | Concentration | 20 mcg | 50 mcg | 100 mcg | 200 mcg | 300 mcg | 500 mcg |
|---|---|---|---|---|---|---|---|
| IGF-1 LR3 0.1 mg + 1 mL | 100 mcg/mL | 20 | 50 | 100 | — | — | — |
| IGF-1 LR3 1 mg + 1 mL | 1,000 mcg/mL | 2 | 5 | 10 | 20 | — | — |
| Sermorelin 5 mg + 2 mL | 2,500 mcg/mL | — | 2 | 4 | 8 | 12 | 20 |
| Sermorelin 10 mg + 2 mL | 5,000 mcg/mL | — | 1 | 2 | 4 | 6 | 10 |
The IGF-1 LR3 figures at 1 mg/mL fall to 2–5 units, where a single unit is 10 mcg. Water volumes for sermorelin are on reconstituting sermorelin, and the mcg to units page gives the formula for any vial.
What is not established
IGF-1 LR3 has no human pharmacokinetic, efficacy or safety data, and its contents as sold have been found to differ from the named molecule in published doping-laboratory analyses. Sermorelin's trial data are in growth-hormone-deficient children, not in adults using it for body composition, and the approved product is no longer sold; compounded or research-market sermorelin is not GEREF. No study has compared or combined the two. Nothing on this page is a dose or a suggestion to use either.
Sources and dates
Opened 2026-11-10: the openFDA Drugs@FDA records for sermorelin (NDA 020443, NDA 019863) and mecasermin (BLA 021839); the DailyMed SPL search for sermorelin (0 records) and the INCRELEX label (published 2026-05-20), sections 2 and 3; ClinicalTrials.gov v2 API searches for sermorelin (42), "IGF-1 LR3" (0) and "LR3-IGF-1" (0); the PubMed abstract of Thorner et al., JCEM 1996 (PMID 8772599); PubChem CID 16132413. The IGF-1 LR3 structure, the doping-laboratory analyses, the diagnostic 1 mcg/kg figure and the circulating ranges are as recorded on this site's sermorelin and IGF-1 LR3 pages (2026-09-18 and 2026-09-20). Weekly totals and units are arithmetic by this site. Corrections go to the contact page.