Same Cell, Different Receptor
Growth hormone secretagogues divide into two families that are routinely lumped together and should not be. Both act on pituitary somatotrophs. They bind different receptors to get there.
GHRH analogues — tesamorelin, CJC-1295 No DAC, sermorelin — bind the GHRH receptor, the physiological receptor for growth-hormone-releasing hormone.
Ghrelin mimetics — ipamorelin, and the broader GHS class — bind GHS-R1a, the ghrelin receptor. Different ligand, different receptor, different endogenous hormone.
Reaching one cell through two doors is precisely why the two are combined, and why a blend of one from each family is a different proposition from a larger dose of either.
Full-Length vs. Truncated GHRH
Within the GHRH family there is a second split, and it is a design choice about how to solve the same problem.
Native GHRH is 44 residues and is cleaved within minutes by DPP-4 at its N-terminus. Two strategies address that:
Truncate it. GHRH(1–29) retains the receptor-binding core and discards the rest. CJC-1295 No DAC is such an analogue, with D-Ala2, Gln8, Ala15 and Leu27 substitutions — the D-Ala2 in particular blocking DPP-4. At 3367.97 g/mol it is a considerably smaller molecule.
Protect it. Tesamorelin keeps all 44 residues and attaches a trans-3-hexenoyl group to the N-terminal tyrosine, which blocks the same cleavage without shortening the peptide. At 5135.86 g/mol it is the largest peptide in our catalog.
That makes tesamorelin a useful comparator for any question about what the C-terminal region contributes, since the truncated analogues simply do not have it.
Why Ipamorelin Specifically
Ipamorelin is a pentapeptide — Aib-His-D-2Nal-D-Phe-Lys-NH2, 711.85 g/mol. Against the 3368 and 5136 g/mol of the GHRH analogues it is a very small molecule, which is part of its appeal as a tool.
The usual reason it is chosen over earlier secretagogues is selectivity. It is described in the literature as selective for GHS-R1a relative to older compounds in the class, with less reported effect on cortisol and prolactin in preclinical work. For an experiment where a confounding endocrine signal would muddy the readout, that matters.
What the Blends Actually Contain
We stock two combinations, and their ratios are worth looking at carefully.
CJC-1295 No DAC + Ipamorelin is an even split — 5 mg of each in the 10 mg vial, 10 mg of each in the 20 mg. On a molar basis that is far from even: 5 mg of CJC-1295 is about 1.5 µmol against 7.0 µmol for the same mass of ipamorelin, a roughly fivefold difference.
Tesamorelin + Ipamorelin is not an even split: 13 mg tesamorelin and 3 mg ipamorelin per 16 mg vial. In molar terms that is about 2.5 µmol against 4.2 µmol — closer to parity than the mass figures suggest, and in the opposite direction from what the labels imply.
This is the general rule with any blend: a 13:3 mass ratio is not a 13:3 molar ratio when the components differ sevenfold in weight. Work from the per-component amounts on the batch certificate.
Designing the Comparison
One receptor assay cannot see both. A GHRH-receptor system will report tesamorelin and CJC-1295 and show ipamorelin as inert. A GHS-R1a system does the reverse. Comparing the families needs both.
Additivity is the usual question. GHRH-receptor and GHS-R1a signalling are reported to act additively in preclinical work, and co-administration is used to probe whether the pathways are independent. A blend answers that only if you also run each component alone — which a fixed-ratio vial cannot give you.
Handle long peptides gently. Tesamorelin at 5136 g/mol is the most aggregation-prone compound in our catalog. Avoid vortexing, introduce diluent down the vial wall, and follow the technique in our peptide reconstitution guide.
Watch the salt form. Tesamorelin's free base is 5135.86 g/mol; acetate-salt listings carry additional mass, around 7.4 acetate equivalents per molecule on at least one vendor entry. A second registry number, 804475-66-9, also circulates alongside CAS 218949-48-5.
An Identity Note on CJC-1295
CJC-1295 No DAC has no widely registered CAS number. The number 863288-34-0 is frequently mis-cited for it; that number refers to CJC-1295 with DAC — a different molecule carrying a Drug Affinity Complex for a much longer half-life.
If a supplier lists a CAS for a no-DAC product, that is a reason to look harder at the rest of the listing, not a reassurance. Confirm identity by mass — 3367.97 g/mol for the no-DAC form — rather than by registry number. Our guide on how to read a peptide COA covers how to read that check.
Frequently Asked Questions
What is the difference between tesamorelin and ipamorelin?
They act on different receptors. Tesamorelin is a GHRH analogue binding the GHRH receptor; ipamorelin is a pentapeptide ghrelin mimetic binding GHS-R1a. Both reach pituitary somatotrophs, by separate routes, which is why they are sometimes combined.
Why use full-length GHRH rather than the 1-29 fragment?
Both solve the same DPP-4 cleavage problem differently — truncation discards everything past the binding core, while tesamorelin's hexenoyl group protects the full 44-residue sequence. Full-length material is the comparator you need for any question about what the C-terminal region contributes.
Is the Tesa/Ipa blend an even split?
No — 13 mg tesamorelin to 3 mg ipamorelin in a 16 mg vial. Because tesamorelin is about sevenfold heavier, the molar amounts are closer than the masses suggest: roughly 2.5 µmol against 4.2 µmol.
What is the CAS number for CJC-1295 No DAC?
There isn't a widely registered one. 863288-34-0 is often mis-cited but refers to CJC-1295 with DAC, a different molecule. Confirm the no-DAC form by its mass of 3367.97 g/mol instead.
References & Further Reading
Falutz J et al., N Engl J Med 2007;357:2359-2370; Stanley TL et al., JAMA 2014;312:380-389; Raun K et al., Eur J Endocrinol 1998;139:552-561; Teichman SL et al., J Clin Endocrinol Metab 2006 (CJC-1295).