What mass should a tesamorelin COA show?

The FDA label gives tesamorelin as C221H366N72O67S with a molecular weight of 5135.9 Da as free base. PubChem gives a monoisotopic mass of 5132.72 Da. A certificate should state the expected and measured values and which kind of mass it compared. A value about 16 higher means oxidised Met27, and a value near 3358 suggests sermorelin, a related but much shorter peptide.

Why does the tesamorelin label mention 2 mg and 2.2 mg?

Because tesamorelin is made as an acetate salt with about seven acetates per molecule. The approved label states each vial contains 2 mg of tesamorelin, equivalent to about 2.2 mg of tesamorelin acetate. The first figure is the peptide, the second includes the acetate. When you compare a test result with a label, check which of the two each one uses.

How do I know if my tesamorelin is real?

Test a sample from your own vial: identity by mass spectrometry, which should find 5135.9 g/mol, then purity by HPLC and an amount against a tesamorelin reference standard. Ask the laboratory to state whether the amount is free base or acetate. Packaging, and certificates for other batches, cannot tell you which peptide is in your vial or how much of it there is.

Can tesamorelin degrade before testing?

Yes. Studies of the parent hormone, GRF(1-44)NH2, found cleavage and rearrangement at aspartic acid 3 and deamidation at asparagine 8 in solution, and tesamorelin also has an oxidation-prone methionine at position 27. Keep the vial sealed, cool and dark until sampling. A test that names these breakdown products tells you more than a single purity number.

Is tesamorelin the same as sermorelin?

No. Sermorelin is the first 29 residues of growth hormone-releasing factor as an amide, about 3357.9 g/mol. Tesamorelin is the full 44-residue sequence with a hexenoyl group added to the first tyrosine, about 5135.9 g/mol. They are related in origin but are different molecules with different masses, which mass spectrometry tells apart immediately.

One of the 30 compound testing profiles

Tesamorelin

Tesamorelin is the 44-amino-acid sequence of human growth hormone-releasing factor with a hexenoyl group on the N-terminal tyrosine (C221H366N72O67S, average mass 5135.9 g/mol as free base); a test should confirm that mass and state whether the amount refers to the peptide or to its acetate salt.

Tesamorelin is a synthetic analogue of human growth hormone-releasing factor and the active ingredient of EGRIFTA SV, a prescription medicine approved by the US FDA (EGRIFTA SV prescribing information, section 11).

Test your tesamorelin

Identity card

Formula: C221H366N72O67S
Average mass: 5,135.9 g/mol
Monoisotopic mass: 5,132.72 Da
Length: 44 residues
Modifications: Hexenoyl group (a C6 chain with a double bond at position 3) on the N-terminal amine of Tyr1; C-terminal amide (leucinamide)
Also sold as: TH9507, Tesamorelin acetate
Sequence: YADAIFTNSYRKVLGQLSARKLLQDIMSRQQGESNQERGARARL
Note: The FDA label gives the free-base formula C221H366N72O67S and a molecular weight of 5135.9 Da, and states that the drug is prepared as an acetate salt with about seven acetates per molecule. PubChem rounds the average mass to 5136 and gives a monoisotopic mass of 5132.7166406 Da, recorded as 5132.72; a doping-control paper lists 5132.7 Da. The sequence string is from PubChem; the C-terminal amide is shown in the doping-control paper's sequence table.

Source: PubChem CID 16137828, Tesamorelin, EGRIFTA SV (tesamorelin) prescribing information, section 11 Description, Knoop A et al. Qualitative identification of growth hormone-releasing hormones in human plasma by LC-HRMS/MS. Anal Bioanal Chem. 2016;408(12):3145-53.

Compare the mass printed on a certificate with the values above. The mass checker explains charge states and which mass a lab usually reports.

What usually goes wrong with tesamorelin. Documented failure modes, with sources.

Peptide or acetate salt: two different milligram figures

The approved label states that tesamorelin is prepared as an acetate salt with about seven acetates per molecule, and that a vial of 2 mg tesamorelin is equivalent to about 2.2 mg of tesamorelin acetate (EGRIFTA SV prescribing information). The approved strength is therefore free base. A research vial may follow either convention, or neither, so a correct vial can look about 10% short or an underfilled one can look correct. An amount report should say which basis it used.

Breakdown at Asp3 and Asn8

Tesamorelin keeps the full 1-44 sequence of human growth hormone-releasing factor. Studies of unmodified GRF(1-44)NH2 in aqueous solution found cleavage at Asp3-Ala4 to give GRF(4-44)NH2, isomerisation of Asp3 to beta-Asp3, and deamidation of Asn8 to beta-Asp8 and Asp8 (Bongers et al., International Journal of Peptide and Protein Research, 1992). Tesamorelin's hexenoyl group sits on Tyr1, but residues 3 and 8 are unchanged, so these are the first places to look. The beta-aspartyl forms keep the parent's mass and need chromatography; cleavage at Asp3-Ala4 removes the first three residues, hexenoyl group included, and is easy to find by mass.

Methionine 27 oxidation

Like the native hormone, tesamorelin carries methionine at position 27, its only sulfur atom (PubChem). Methionine is the residue most susceptible to oxidation; the sulfoxide adds 16 Da and the sulfone 32 Da (Butré et al., Molecules, 2023). A certificate that names oxidised tesamorelin as an impurity shows more than one that gives only a total purity.

Another GRF peptide under the tesamorelin name

Tesamorelin, sermorelin and modified GRF analogues share a parent sequence, but not a mass: a doping-control method lists sermorelin at a monoisotopic mass of 3355.8 Da and tesamorelin at 5132.7 Da, and monitored tesamorelin as a 7+ ion near m/z 734 (Knoop et al., Analytical and Bioanalytical Chemistry, 2016). The 44-residue hormone without the hexenoyl group also has a different formula. A certificate should report the deconvoluted mass, not only a raw m/z value.

Counter-ions that are not acetate

The approved drug is an acetate salt, but peptides straight from solid-phase synthesis are usually trifluoroacetate salts, and the number of counter-ions follows the number of positive charges; in one study trifluoroacetate reached up to 35% of the weight of the peptide salts tested (Erckes et al., Pharmaceuticals, 2025). Tesamorelin carries six arginines and two lysines, so a research vial that skipped salt exchange may hold a heavy trifluoroacetate load, which only a counter-ion measurement shows.

Which tests matter most

LC-MSConfirms 5135.9 g/mol and separates tesamorelin from sermorelin, non-acylated GRF(1-44) and the GRF(4-44) cleavage product.
HPLC-UVGives purity and resolves same-mass beta-Asp3 and beta-Asp8 forms from the parent.
Counter-ion contentThe approved drug is an acetate salt with about seven acetates; measuring them lets the amount be stated as free base.
HRMSAccurate mass near 5132.72 Da monoisotopic separates the Asn8 deamidation product, only +0.984 Da away.
Peptide mappingPlaces the hexenoyl group on Tyr1 and locates any oxidation at Met27 or change at Asp3 and Asn8.

Reading tesamorelin results

The approved product is a lyophilised powder holding 2 mg of tesamorelin with histidine, mannitol, polysorbate 20 and sucrose as inactive ingredients (EGRIFTA SV prescribing information), so an approved vial and a research vial give different chromatograms. The net peptide content lesson explains why free base, acetate and purity figures differ for the same vial.

Public Tested.ph results

No public tesamorelin records yet

Each public tesamorelin record will appear here with its identity, HPLC purity and measured amount against the label, once the first vial is tested.

FIG 13Amount against the label

Questions about testing tesamorelin

What mass should a tesamorelin COA show?: The FDA label gives tesamorelin as C221H366N72O67S with a molecular weight of 5135.9 Da as free base. PubChem gives a monoisotopic mass of 5132.72 Da. A certificate should state the expected and measured values and which kind of mass it compared. A value about 16 higher means oxidised Met27, and a value near 3358 suggests sermorelin, a related but much shorter peptide.
Why does the tesamorelin label mention 2 mg and 2.2 mg?: Because tesamorelin is made as an acetate salt with about seven acetates per molecule. The approved label states each vial contains 2 mg of tesamorelin, equivalent to about 2.2 mg of tesamorelin acetate. The first figure is the peptide, the second includes the acetate. When you compare a test result with a label, check which of the two each one uses.
How do I know if my tesamorelin is real?: Test a sample from your own vial: identity by mass spectrometry, which should find 5135.9 g/mol, then purity by HPLC and an amount against a tesamorelin reference standard. Ask the laboratory to state whether the amount is free base or acetate. Packaging, and certificates for other batches, cannot tell you which peptide is in your vial or how much of it there is.
Can tesamorelin degrade before testing?: Yes. Studies of the parent hormone, GRF(1-44)NH2, found cleavage and rearrangement at aspartic acid 3 and deamidation at asparagine 8 in solution, and tesamorelin also has an oxidation-prone methionine at position 27. Keep the vial sealed, cool and dark until sampling. A test that names these breakdown products tells you more than a single purity number.
Is tesamorelin the same as sermorelin?: No. Sermorelin is the first 29 residues of growth hormone-releasing factor as an amide, about 3357.9 g/mol. Tesamorelin is the full 44-residue sequence with a hexenoyl group added to the first tyrosine, about 5135.9 g/mol. They are related in origin but are different molecules with different masses, which mass spectrometry tells apart immediately.

Sources

EGRIFTA SV (tesamorelin) prescribing information, DailyMed, US National Library of Medicine
Bongers J et al. Degradation of aspartic acid and asparagine residues in human growth hormone-releasing factor. Int J Pept Protein Res. 1992;39(4):364-74, PubMed
Butré CI et al. Interlaboratory Evaluation of a User-Friendly Benchtop Mass Spectrometer. Molecules. 2023;28(6):2855, Molecules (PMC)
Knoop A et al. Qualitative identification of growth hormone-releasing hormones in human plasma by LC-HRMS/MS. Anal Bioanal Chem. 2016;408(12):3145-53, Analytical and Bioanalytical Chemistry (PMC)
PubChem CID 16137828, Tesamorelin, National Library of Medicine
Erckes V et al. Towards a Consensus for the Analysis and Exchange of TFA as a Counterion in Synthetic Peptides. Pharmaceuticals. 2025;18(8):1163, Pharmaceuticals (PMC)

Last reviewed 6 Oct 2026.