HPLC · CoA
Tesamorelin vs Ipamorelin: What Is the Difference?
Comparison · 7 min read · Updated 30 September 2026
The difference between tesamorelin vs ipamorelin is the receptor each one activates. Tesamorelin is a full-length 44 residue GHRH analogue that binds the GHRH receptor on pituitary somatotrophs and raises cyclic AMP. Ipamorelin is a five residue synthetic agonist of the ghrelin receptor, GHS-R1a, which signals through intracellular calcium. Both trigger growth hormone release in laboratory models, but from opposite sides of the control system, which is why they are studied alone, compared, or paired to examine receptor synergy.
We supply both as single vials and as a fixed-ratio blend. The right choice depends on the receptor question a protocol asks, so the comparison starts with structure and works outward to vial arithmetic.
Which Receptors Do Tesamorelin and Ipamorelin Act On?
Tesamorelin acts on the GHRH receptor and ipamorelin on the ghrelin receptor, two of the three main inputs that govern pituitary growth hormone cells. The first stimulatory input is GHRH from the hypothalamus. The second is ghrelin, a 28 residue acylated hormone produced mainly in the stomach. The inhibitory input is somatostatin. Synthetic growth hormone releasing peptides, the GHRP family, were described in the 1980s before ghrelin itself was known; their receptor was cloned in 1996 and ghrelin was identified as its endogenous ligand in 1999.
- **GHRH receptor:** a class B G protein coupled receptor. Activation couples to Gs, raises cyclic AMP and drives both release and new synthesis of growth hormone.
- **Ghrelin receptor (GHS-R1a):** a class A receptor. Activation couples to Gq, stimulates phospholipase C and increases intracellular calcium. It is also expressed in the hypothalamus, where it appears to reduce somatostatin tone.
Because the two routes use different second messengers, stimulating both in pituitary models produces a larger growth hormone signal than either alone. That synergy explains why GHRH analogues and ghrelin agonists are so often paired in research designs.
What Is Tesamorelin?
Tesamorelin is human GHRH with all 44 residues retained and a trans-3-hexenoyl group attached to the position 1 tyrosine. Tesamorelin in 2mg, 5mg, 10mg and 20mg research vials has a molecular weight of about 5,136 daltons. The six-carbon cap blocks dipeptidyl peptidase-4, the protease that strips residues 1 and 2 from native GHRH and inactivates it within minutes. Unlike the 1-29 analogues, it carries the complete native sequence, so its receptor behaviour remains close to that of the natural hormone.
It is also the most clinically documented compound in its class. Its phase 3 programme was reported in NEJM in 2007, and it was licensed in the United States in 2010 for one narrow indication. It holds no Australian registration, and we supply it strictly as a laboratory reagent.
What Is Ipamorelin?
Ipamorelin is a selective ghrelin receptor agonist built as a five residue chain, Aib-His-D-2-Nal-D-Phe-Lys-NH2. Ipamorelin as a 10mg lyophilised vial weighs about 712 daltons. Three of its five residues are unnatural, which gives it resistance to peptidases despite its small size. It was introduced in a 1998 European Journal of Endocrinology report as the first selective growth hormone secretagogue: in the swine model used, growth hormone rose while ACTH and cortisol remained flat, in contrast to the response to GHRP-6 and GHRP-2. That selectivity is the property most studies choose it for.
Why Does the Size Difference Matter at the Bench?
The size difference matters because weight-matched solutions of the two peptides contain very different numbers of molecules. Tesamorelin is roughly seven times heavier than ipamorelin. One milligram of tesamorelin is about 0.19 micromoles; one milligram of ipamorelin is about 1.4 micromoles. Where receptor occupancy is the question, set and report concentrations on a molar basis.
Tesamorelin vs Ipamorelin at a Glance
| Property | Tesamorelin | Ipamorelin |
|---|---|---|
| Class | GHRH analogue | Ghrelin receptor agonist (GHRP family) |
| Length | 44 residues | 5 residues |
| Molecular weight | about 5,136 Da | about 712 Da |
| Receptor | GHRH receptor | GHS-R1a |
| Main signalling route | Gs, cyclic AMP | Gq, phospholipase C, calcium |
| Protection from breakdown | Hexenoyl cap blocks DPP-4 | Unnatural residues resist peptidases |
| Key literature | Phase 3, NEJM, 2007 | European Journal of Endocrinology, 1998 |
| Sizes we stock | 2mg, 5mg, 10mg, 20mg | 10mg |
| Typical research use | GHRH receptor pharmacology, full-length analogue work | Selective ghrelin receptor activation without ACTH signalling |
Can Tesamorelin and Ipamorelin Be Combined in One Vial?
Tesamorelin and ipamorelin are chemically compatible and can share one vial, and we supply them co-lyophilised as a 13mg plus 3mg blend. The Tesamorelin and Ipamorelin 13+3mg vial holds 16mg of peptide in a single cake. The ratio is 13 to 3 by weight, but the molar picture differs: 13mg of tesamorelin is about 2.5 micromoles, while 3mg of ipamorelin is about 4.2 micromoles, so ipamorelin molecules outnumber tesamorelin molecules by roughly 1.7 to 1.
| Water added | Combined strength | Tesamorelin | Ipamorelin | Per unit on a U-100 syringe |
|---|---|---|---|---|
| 2 mL | 8 mg per mL | 6.5 mg per mL | 1.5 mg per mL | 65 mcg plus 15 mcg |
| 2.5 mL | 6.4 mg per mL | 5.2 mg per mL | 1.2 mg per mL | 52 mcg plus 12 mcg |
| 3 mL | 5.33 mg per mL | 4.33 mg per mL | 1 mg per mL | 43.3 mcg plus 10 mcg |
| 4 mL | 4 mg per mL | 3.25 mg per mL | 0.75 mg per mL | 32.5 mcg plus 7.5 mcg |
Each unit is 0.01 mL, so the per-unit figures are one hundredth of the mg per mL values, given in micrograms. Reconstitute with bacteriostatic water for multi-day stocks and keep the mixed vial refrigerated at 2 to 8 °C.
How Does CJC-1295 + Ipamorelin Compare With Tesamorelin?
The CJC-1295 + ipamorelin pairing differs from tesamorelin mainly in its GHRH component, since both combinations can use the same ghrelin agonist. The CJC-1295 no DAC and ipamorelin blend uses modified GRF 1-29, a truncated 29 residue chain with four substitutions and a mass near 3,368 daltons. Tesamorelin carries all 44 residues and a fatty acid cap. A study asking whether the missing 15 residues alter receptor behaviour, or one that needs the analogue with the deepest clinical record, points to tesamorelin. A study that only needs a stabilised GHRH signal alongside ipamorelin can use either.
Which Peptide Fits a Given Research Protocol?
The correct peptide is set by the receptor pathway under study, as the following decision list shows.
- GHRH receptor and cyclic AMP pathway only: tesamorelin alone
- Ghrelin receptor signalling without ACTH or cortisol confounds: ipamorelin alone
- Receptor synergy at a fixed ratio from one lot: the 13+3mg blend
- Attribution of each effect to one receptor: two single vials, run as separate arms and then together
Our recommendation is to begin with the two single vials whenever a study design is new. They establish each compound's signal independently before combination, and the blend becomes a convenience once the combined design is fixed. The full set of releasing hormone analogues and secretagogues is listed in our growth hormone research category.
Questions about tesamorelin vs ipamorelin
Sources
- Ipamorelin, the first selective growth hormone secretagogue. European Journal of Endocrinology. 1998.
- A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996.
- Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999.
Written by the Macropus Peptides technical team for in-vitro laboratory research reference. Not medical advice; products are not for human or veterinary use and are sold to buyers aged 18 and over.