Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Informational only. Not medical advice.INFORMATIONAL PLATFORM ONLY — NOT MEDICAL ADVICE, DIAGNOSIS, OR TREATMENT
Head-to-head comparison of IGF-1 LR3 and Sermorelin — mechanism, dosing, side effects, legal status, and pricing.
IGF-1 LR3 is an 83-amino-acid modified IGF-1 analog with a 13-residue N-terminal extension (MFPAMPLSSLFVN) and an Arg-3 substitution. These modifications reduce binding to IGF binding proteins (IGFBPs), extending effective half-life and increasing tissue bioavailability relative to native IGF-1. It is a research/cell-culture reagent and is NOT FDA-approved for any human use. Do not confuse with mecasermin (Increlex), which is recombinant human IGF-1 and IS FDA-approved for severe primary IGF-1 deficiency.
Sermorelin is a synthetic analog of growth hormone-releasing hormone (GHRH) consisting of the first 29 amino acids of the 44-aa native hormone — the shortest fragment that retains full biological activity. It was FDA-approved in the 1990s as Geref (EMD Serono) for diagnostic testing of pituitary GH reserve and later for pediatric idiopathic GH deficiency, but was withdrawn from the US market in 2008–2009 at the manufacturer's request for commercial reasons (not safety or efficacy). It remains on the FDA Category 1 list of bulk substances nominated for use in 503A compounding, where it is now widely prescribed off-label for adult GH insufficiency and "anti-aging" indications.
IGF-1 LR3
Sermorelin
Category
Legal Status
Mechanism
Dose Range
Route
Frequency
COA-verified vendors · trust score ≥70 required · single-vial price — bulk/bundle deals may be lower
IGF-1 LR3
Sermorelin
COA corpus from Disclosed Labs — independently tested batches only.
IGF-1 LR3
42
COAs
98.7%
Avg purity
9
Labs
Sermorelin
72
COAs
99.4%
Avg purity
10
Labs
Sermorelin is among peptides under FDA review for the Category 1 (503A) list; if added, it would require a prescription to be compounded by registered 503A/503B pharmacies — not yet authorized. IGF-1 LR3 remains research-only. In April 2026 the FDA removed 12 peptides from Category 2, which does not place them on the Category 1 list or authorize compounding. The FDA's Pharmacy Compounding Advisory Committee is advisory and meets July 23–24, 2026 to review nominations and make recommendations to the FDA.
Francis et al. (J Mol Endocrinol 1992; PMID 1378742) characterized LR3-IGF-1 as a fusion analog whose enhanced biological potency derives from reduced IGFBP binding; in IGFBP-free cell systems LR3 was actually LESS potent than native IGF-1, underscoring that the 'potency' is really reduced sequestration rather than intrinsically stronger receptor activation. Tomas (Growth Horm IGF Res 2001; PMID 11472075) infused LR(3)IGF-I into food-restricted rats and found it preserved body weight and nitrogen retention but did NOT conserve skeletal muscle protein — which contradicts the common 'potent muscle builder' framing from preclinical literature alone. There are no controlled human trials supporting bodybuilding use. Epidemiologic and mechanistic work reviewed by Grimberg (Cancer Biol Ther 2003; PMID 14688466) links elevated IGF-1 axis activity to breast, prostate, and colorectal cancer risk, so chronic systemic LR3 exposure carries a concrete — not merely theoretical — tumorigenesis concern. IGF-1 and its analogs are banned at all times under the WADA Code.
Key references
Sermorelin was FDA-approved in the 1990s as Geref for the GHRH stimulation test of pituitary function and, at higher doses, for pediatric idiopathic GHD. The principal review of pediatric Geref data is Prakash & Goa (BioDrugs 1999; PMID 18031173). In adults, Vittone et al. (Metabolism 1997; PMID 9005976) showed nightly sermorelin in healthy elderly men raised IGF-1 and modestly increased lean mass, and Khorram, Laughlin & Yen (J Clin Endocrinol Metab 1997; PMID 9141536) demonstrated that 16 weeks of nightly [Nle27]GHRH(1-29) in 19 subjects aged 55-71 restored GH/IGF-1 toward young-adult levels with small gains in lean mass and skin thickness. Walker (Clin Interv Aging 2006; PMID 18046908) reviewed the rationale for sermorelin as a more physiologic alternative to rhGH in adult GH insufficiency. EMD Serono discontinued Geref in 2008; FDA withdrew NDA approvals in 2009 and affirmed in 2013 that this was for commercial — not safety or efficacy — reasons. Unlike exogenous GH, sermorelin has not been associated with reports of acromegaly because endogenous feedback limits peak GH.
IGF-1 LR3 and Sermorelin are both in the Performance category and may have overlapping mechanisms. Researchers should review both profiles carefully, understand the mechanisms of action, and monitor the relevant biomarkers when combining compounds in the same class. As always, consult a licensed healthcare provider before making any decisions about combining research compounds.
This platform provides informational tools only, not medical advice. This comparison is for educational purposes only. Consult a licensed provider.
Dosing Notes
Half-life
Side Effects
Contraindications
Lab Testing
Key references
Disclosed Labs