Tesamorelin and Ipamorelin are both synthetic peptides that the Prototides catalog groups under Growth Factors. On paper they are separated by roughly an order of magnitude in molecular mass, which is the most consequential practical difference between them when reviewing documentation. This reference compares what each molecule is and how each lot is characterized and documented.
It does not compare — and does not describe or imply — any biological effect, activity, outcome, or application of either compound, and neither is presented as preferable to the other. Both are supplied strictly for laboratory research use.
At a Glance
Reference values for each molecule. Lot-specific figures are always those printed on the accompanying Certificate of Analysis, which takes precedence over any general reference.
| Attribute | Tesamorelin | Ipamorelin |
|---|---|---|
| CAS number | 218949-48-5 | 170851-70-4 |
| Molecular formula | C221H362N64O68S | C38H49N9O5 |
| Reported mass | ~5135.8 Da | ~711.9 Da |
| Sequence length | 44 residues | 5 residues (pentapeptide) |
| Structural basis | Stabilized analog of growth-hormone-releasing factor (GRF/GHRH) | Synthetic pentapeptide with amidated C-terminus; growth-hormone secretagogue class |
| Category | Growth Factors | Growth Factors |
| Identity method | LC-MS | LC-MS |
| Purity method | RP-HPLC (area %) | RP-HPLC (area %) |
| Physical form | White lyophilized powder | White lyophilized powder |
| Storage | -20 °C, protected from light | -20 °C, protected from light |
| Classification | Research use only | Research use only |
How the Molecules Differ Structurally
Tesamorelin is a forty-four-residue peptide of approximately 5135.8 Da. Structurally it is a stabilized analog of growth-hormone-releasing factor, carrying an N-terminal modification relative to the native sequence; its formula includes sulfur, reflecting a sulfur-containing residue. Ipamorelin is far smaller — a five-residue pentapeptide of approximately 711.9 Da terminating in a C-terminal amide, described in the research literature as a growth-hormone secretagogue-class peptide.
Those class descriptions are structural and receptor-target categories drawn from the literature; they are noted here without any associated effect claim. Both are fully defined synthetic sequences assembled by solid-phase peptide synthesis. For the full per-compound treatment, see the Tesamorelin research profile and the Ipamorelin research profile.
How Each Is Characterized
The analytical approach is identical for both:
- RP-HPLC separates the target peptide from synthesis-related impurities and reports purity as an area-percent value for the tested sample under a stated method.
- LC-MS confirms identity by measuring molecular mass and comparing it to the theoretical value calculated from the sequence.
The size gap changes the burden, not the method. Tesamorelin's forty-four-residue chain presents substantially more opportunity for synthesis-related impurities than Ipamorelin's five, and its mass confirmation is checked against a theoretical value more than seven times larger. Conversely, Ipamorelin's low molecular mass means a laboratory calculates working concentrations from a much smaller mass per mole. The distinction between purity and identity is covered in how identity and purity are verified.
Documentation — Identical Standard
Both compounds follow the same catalog-wide documentation standard. Each lot ships with:
- A Certificate of Analysis recording the lot's purity result, mass confirmation, and release date — see the guide to Certificates of Analysis.
- The RP-HPLC purity report supporting the figure on the COA.
- An independent third-party analytical report from a separate laboratory.
A unique lot identifier ties these records to the physical container, as described in batch traceability and lot documentation. Because the standard is shared, the two compounds' records can be read side by side using the same criteria.
Storage and Handling
Both are supplied as lyophilized powder, stored at -20 °C and protected from light. The freeze-dried solid is the stable reference form for each; once reconstituted with a solvent appropriate to the protocol, common laboratory practice for both is to divide the stock into single-use aliquots and minimize freeze–thaw cycles. Reconstitution solvent, working concentration, and storage of any prepared solution are determined by the researcher against the requirements of the specific experiment — see cold-chain and -20 °C storage.
What This Comparison Does and Does Not Establish
This is a structural and documentation reference. It does not, on its own, establish any of the following:
- That either compound is more effective, more suitable, or preferable to the other — no effect or activity is claimed for either, so no such comparison is possible or intended.
- Any biological effect, activity, or outcome for either material — none is claimed or implied.
- That either material is appropriate for a specific research workflow — suitability is a laboratory determination made against institutional SOPs.
- Fitness for human or veterinary use, diagnosis, treatment, or consumption. Both are supplied for laboratory research use only.
Key Takeaways
- Tesamorelin (44 residues, ~5135.8 Da) and Ipamorelin (5 residues, ~711.9 Da) differ by roughly an order of magnitude in molecular mass.
- Both are characterized by the same two methods — RP-HPLC for purity, LC-MS for identity — with chain length changing the analytical burden, not the approach.
- Both carry an identical documentation standard: COA, RP-HPLC report, and independent third-party report tied by a lot identifier.
- This reference compares molecules and records only. No effect, activity, or superiority is claimed or implied for either.
