Molecule guides
Tesamorelin + Ipamorelin: Full-Length Acyl-Capped GHRH With a Selective Secretagogue
How the N-terminal cap protects the peptide, why a 2:1 weight ratio is nothing like 2:1 in moles, and the questions a blend certificate has to settle.
Key facts
- CAS number: Tesamorelin: 218949-48-5 · Ipamorelin: 170851-70-4
- Molecular formula: Tesamorelin: C221H366N72O67S · Ipamorelin: C38H49N9O5
- Molecular weight: Tesamorelin: 5135.86 g/mol · Ipamorelin: 711.85 g/mol
- Purity: ≥99% by HPLC per component; lot-matched COA available
- Form: Co-lyophilized powder, sealed glass vial
- Storage: Lyophilized: −20 °C, protected from light and moisture. Reconstituted: 2–8 °C, use within the study window.
- Available sizes: 15 mg · (10/5) · 30 mg · (20/10)
This tesamorelin and ipamorelin preparation is freeze-dried as a 2:1 mixture by weight, putting a stabilised full-length GHRH analogue together with a selective five-residue ghrelin receptor agonist. The GHRH partner is what marks it out among growth hormone blends: tesamorelin reproduces all 44 residues of human GHRH and carries a trans-3-hexenoyl group at its N-terminus, and no other GHRH-side compound in this category can point to both an authorised prescription reference product and published Phase 3 data — those data being in the reduction of visceral fat in HIV-associated lipodystrophy. The authorisation belongs to the prescription medicine, not to research-grade substance, and that distinction runs through everything that follows.
Our tesamorelin and ipamorelin blend is supplied as a co-lyophilized powder in two presentations — 15 mg (10 mg/5 mg) and 30 mg (20 mg/10 mg) — listed with the growth hormone blends.
Where each component comes from
Where sermorelin and the CJC-1295 compounds are based on the 29-residue active fragment, tesamorelin keeps the entire 44-residue human growth hormone releasing hormone sequence. Its single alteration is chemical, not a substitution: a trans-3-hexenoyl group attached at the N-terminus. That cap protects the molecule's most vulnerable bond — Tyr1-Ala2, the site DPP-4 attacks — while leaving every residue as it is in the native hormone. The chemistry is described in our tesamorelin explainer, and tesamorelin vs sermorelin weighs it against the shorter fragment.
The pentapeptide ipamorelin emerged from Novo Nordisk's 1990s work on secretagogues, built around D-2-naphthylalanine and aminoisobutyric acid residues. Its published claim to distinction is selectivity: in both animal and human pharmacology it was described as releasing growth hormone without the cortisol, ACTH and prolactin increases typical of the GHRP-2, GHRP-6 and hexarelin generation. Our ipamorelin explainer has the details.
Why the two are combined
Pairing them makes sense because the two receptors sit on the same pituitary cell and use different second messengers. GHRH receptor agonism, via Gs, pushes up cAMP and activates protein kinase A. Ghrelin receptor agonism, via Gq, brings in phospholipase C, produces IP3 and raises cytosolic calcium. Studies in animals and in people that gave a GHRH-class compound together with a GHRP-class one have consistently found a greater secretory response than either alone, and GHS-R1a agonists have additionally been described as easing somatostatin restraint, which would allow a fuller GHRH-driven response.
Two constraints follow from this specific formulation. First, two-to-one by weight is not two-to-one by moles. At 5,135.86 g/mol against 711.85 g/mol, 10 mg of tesamorelin comes to roughly 1.95 µmol whereas 5 mg of ipamorelin comes to roughly 7.02 µmol — about 3.6 molar parts of ipamorelin for each part of tesamorelin. Second, freeze-drying the two together fixes that proportion, so changing it requires buying separate Tesamorelin and Ipamorelin vials. Our guide to blends against single vials explains when each format makes sense.
What has been studied
Visceral adipose tissue and the approved indication
Tesamorelin has by far the best human evidence base of any GHRH-side compound in this category. In Phase 3 work involving patients who had HIV-associated lipodystrophy, CT imaging showed visceral fat decreasing, with accompanying shifts in IGF-1 and triglycerides; the prescription product was authorised on the strength of those findings. Note carefully what that evidence covers: a medicine prescribed and supervised by clinicians. It is not evidence about this blend, nor about research-grade substance of any kind.
Liver fat and metabolic endpoints
Later investigator-initiated studies in the same patient population looked at liver fat fraction and related metabolic markers, again with the licensed product. That is the work which explains why tesamorelin shows up in metabolic research contexts and not only in growth-axis ones.
Combined GHRH and secretagogue pharmacology
Behind the pairing rationale lies a separate, older literature in which GHRH was given together with a GHRP-class secretagogue to animals and to human volunteers, with synergy at the pituitary reported. Those studies generally used native GHRH or sermorelin rather than tesamorelin.
Ipamorelin selectivity work
In preclinical comparisons against GHRP-6, the pentapeptide triggers growth hormone release without the accompanying ACTH and cortisol rise — the reason it is the secretagogue chosen for most blends sold today.
What has not been studied
This co-formulation has not been the subject of any published controlled study, and nothing shows a 2:1 weight ratio to be optimal for any research purpose. The composition is a convention of formulation.
Presentations available
Each size arrives with both peptides freeze-dried into a single vial, so one reconstitution yields a solution at the stated proportion. For a shorter run of experiments, take the 15 mg presentation (10 mg plus 5 mg); for a long study that ought to stay on one batch, the 30 mg presentation (20 mg plus 10 mg) is the cheaper route. A certificate accompanies every batch, reporting purity per peptide at 99% or better by HPLC. Where the licensed medicine rather than the research compound is what you need, the relevant listing is Tesamorelin (Egrifta-type), available on prescription only.
Reconstitution and storage at the bench
Treat the blend as one material when reconstituting. Choose bacteriostatic water if you will draw from the vial repeatedly, or sterile water where a preservative would disturb the assay. Let the solvent run down the inside of the glass and swirl, don't shake: tesamorelin is a 44-mer, and shaking adds foam and surface denaturation without speeding dissolution at all.
Because this is not a 1:1 blend, do the sums one peptide at a time. Take the 15 mg presentation (10 mg plus 5 mg) up in 2 mL: total concentration 7.5 mg/mL, of which tesamorelin is 5 mg/mL and ipamorelin 2.5 mg/mL. Draw 0.1 mL — ten units on a U-100 scale — and you have 500 micrograms of the GHRH analogue plus 250 mcg of the pentapeptide. Reading the combined number as if one peptide were involved is where blend calculations usually go wrong. The reconstitution guide sets out the method.
Sealed freeze-dried vials belong in a −20 °C freezer, dry and shielded from light. Solution keeps at 2–8 °C across a study window; for programmes running longer than that, divide it into aliquots and freeze them. See how to store peptides for the general rules.
Purity and reading a blend certificate
For a product with two peptides in it, the paperwork has to answer two questions: which peptides, and in what proportion. Purity figures belong to each peptide individually — a single merged number is not informative. Mass spectrometry should report both masses, 5,135.86 g/mol and 711.85 g/mol; as a pair they pin identity far more firmly than one value could, and since the two are so far apart their peaks are easy to tell apart. The chromatogram should show two peaks, clearly separated, with areas that fit a blend of two parts to one by weight. If you see only one peak, or areas that contradict the label, raise it with the supplier before using the vial.
Regulatory position
On this point tesamorelin is unusual among research peptides. A licensed prescription product built on the same molecule is available in the United States for a single specified indication: a biologic, prescription-only, dispensed by pharmacies with medical oversight. Nothing about that extends to the research-grade blend described here, which is a different article and holds no approvals of its own. Ipamorelin, for its part, is not authorised as a medicine in any country. Sporting anti-doping codes prohibit secretagogues and GHRH analogues alike.
Related blends and further reading
Alternatives that keep ipamorelin and swap the GHRH partner: CJC-1295 (No DAC) + Ipamorelin combines it 1:1 with a 29-residue analogue bearing four substitutions, while Sermorelin + Ipamorelin uses the native, unmodified GHRH (1-29) fragment.
Matching catalogue section: Growth Hormone Blends
Questions
What sets tesamorelin apart from other GHRH analogues?
Two features. First, it uses the complete 44-residue human GHRH sequence rather than the shorter 29-residue active fragment. Second, its only alteration is a trans-3-hexenoyl cap at the N-terminus, which prevents DPP-4 cleavage. No residue is swapped, so the sequence itself matches native GHRH throughout.
In a 2:1 blend, are there two moles of tesamorelin for each mole of ipamorelin?
The opposite is true. Their masses are 5,135.86 and 711.85 g/mol, so 10 mg of the GHRH analogue is about 1.95 µmol and 5 mg of the pentapeptide about 7.02 µmol — near 3.6 moles of ipamorelin for each mole of tesamorelin. Ratios printed on blend labels are always by weight.
How does the reconstitution arithmetic work for an unequal blend?
One peptide at a time. Reconstituting the 15 mg presentation (10 mg plus 5 mg) with 2 mL gives 7.5 mg/mL overall: 5 mg/mL of the GHRH analogue and 2.5 mg/mL of the pentapeptide, so 0.1 mL holds 500 mcg and 250 mcg respectively. Treating the combined mass as a single peptide is the classic error.
Has tesamorelin been approved?
In the United States, a prescription medicine containing tesamorelin is licensed for one specific indication and is dispensed through pharmacies under medical supervision. Research-grade material is a separate article entirely: not equivalent to it, and covered by none of those approvals.
Why is ipamorelin the secretagogue chosen for these blends?
Selectivity is the reason. In preclinical comparisons against GHRP-6, ipamorelin released growth hormone without triggering the ACTH and cortisol response that the older GHRP compounds cause — a cleaner partner when the GHRH side is the variable under study.
What should the certificate show?
Purity for each peptide on its own instead of one merged figure; mass spectrometry that confirms 5,135.86 and 711.85 g/mol; and a chromatogram showing two well-separated peaks with areas fitting a two-parts-to-one blend by weight. If the proportion does not match the label, take it up with the supplier.
How does it compare with CJC-1295 + Ipamorelin?
All of them put ipamorelin with a GHRH-side compound, but those compounds differ in length, in how they are stabilised and in how much evidence stands behind them — acyl-capped full-length GHRH(1-44) in this case, against a 29-residue fragment with four substitutions — and the weight ratios differ too: 2:1 here, 1:1 there.