hGH testing: what a lab test shows for identity, content, purity and dimers

What an hGH test should show

An hGH test should show four things: that the vial holds somatropin, how many mg it holds, how pure it is, and how much of it has clumped into dimers or larger aggregates. The fourth needs its own method. This guide is about what is in a vial; a blood test for growth hormone levels is a medical test.

Question	Method	Reported as
Is it hGH?	Intact mass by LC-MS; peptide mapping for the sequence	Observed vs expected mass
How much is in the vial?	Quantitative HPLC or SEC against a somatropin reference standard	mg per vial; IU only with the factor stated
How pure is it?	Reversed-phase HPLC	% peak area, with the chromatogram
How much has clumped?	Size-exclusion chromatography (SEC)	Dimer and larger aggregates as % of total
Endotoxin	LAL	EU per mg and per vial
Sterility	USP <71>, 14 days	Growth or no growth

hGH is a 191-amino-acid protein

Somatropin has 191 amino acids, a relative molecular mass of 22,125 and the formula C990H1528N262O300S7, according to the European Pharmacopoeia’s somatropin monographs (6th edition text). UniProt records two disulfide bridges in the chain. The pharmacopoeia’s HPLC tests for somatropin use wide-pore (30 nm) columns, so ask whether a lab’s hGH method was developed for a protein of this size.

Do not confuse it with “hGH fragment 176-191”, a 16-amino-acid peptide sold under a similar name. Labs list it as a separate test: Chromate as “hGH frag 176-191”, Janoshik as “rHGH fragment or AOD-9604”. A mass measurement tells the two apart at once.

Identity: is it somatropin?

An LC-MS identity test of a protein this size sees many charge states, which software combines into one mass close to 22,125. Deamidation and similar small changes barely move that mass, so intact mass confirms the molecule and HPLC finds the variants. Our guide to LC-MS identity explains the mass match.

The pharmacopoeia uses four identification tests: capillary electrophoresis, the HPLC retention time, the SEC retention time and a peptide map. In a peptide map, trypsin cuts the protein into fragments, and the pattern must match a digest of the reference standard.

Content: mg, IU and the conversion factor

hGH labels may state IU, mg or both. The European Pharmacopoeia sets a labelling convention: 1 mg of anhydrous somatropin is equivalent to 3.0 IU. The EMA product information for one licensed product follows it: 5 mg of somatropin corresponds to 15 IU. So a vial labelled 10 IU should hold about 3.33 mg.

IU on a label is a conversion from mg; it does not measure biological activity. A lab measures mg against a somatropin reference standard and converts; in the pharmacopoeia, the content assay is the SEC run itself. The report should print the mg per vial with its basis (anhydrous somatropin), the reference standard, the IU factor if IU is printed, and the % of the label claim.

For scale, the pharmacopoeia requires somatropin for injection, the freeze-dried medicine, to hold 89.0% to 105.0% of the stated somatropin. It also allows buffers and stabilisers in the vial, so powder weight is not hGH weight. See net peptide content and how a content per vial result is reported.

Purity: related proteins by HPLC

Reversed-phase HPLC separates forms that differ slightly from somatropin, such as deamidated forms. The pharmacopoeia method uses a butyl (C4) column with detection at 220 nm. Deamidated somatropin elutes at about 0.85 of the main peak’s retention time. For the bulk active substance, the limit is 6.0% related proteins in total. A separate electrophoresis test limits deamidated forms to 5.0%.

A single “purity” figure on a research COA is usually one HPLC peak area share. Read it with its wavelength and chromatogram, as our guide to what purity means explains.

Size variants: hGH dimers by SEC

SEC separates molecules by size: dimers and larger aggregates leave the column before the single protein. In the pharmacopoeia method, larger aggregates elute at about 0.65 and the dimer at about 0.9 of the monomer’s retention time, with detection at 214 nm. For the bulk active substance, all peaks eluting before the monomer may total no more than 4.0%.

Heat creates dimers. The pharmacopoeia makes its test mixture by heating the reference standard at 50 °C for 12 to 24 hours, to generate 1% to 2% dimer. Its storage text for the bulk solution says to avoid repeated freezing and thawing. A vial that sat in heat may therefore show more dimer than it left the factory with. Our peptide degradation guide covers aggregation.

An SEC result shows the size distribution. It cannot show biological activity.

Labs that list hGH testing

We read each lab’s own pages (archived copies for Analiza Białek) in September 2026.

Lab	What it lists for hGH	Dimer or size variants
Janoshik	“Human Growth Hormone amount and purity”	A second test adds “dimer and higher molecular weight proteins”
Chromate	“hGH (191aa)”	“hGH w/ dimer” as its own test; its July 2024 page described SEC-HPLC with dimer and larger-protein detection
Krause Analytical	HGH (Somatotropin) on its compound list; peptide tests by HPLC-UV and HPLC-MS	Not stated
Analiza Białek	hGH analysis as its own category; HPLC-DAD against reference standards	Not stated
Testides	HGH on its compound list; HPLC-DAD with retention-time and UV-spectrum match, MS when the question requires it	Not stated
Freedom Diagnostics	Does not accept hGH, HCG, HMG or testosterone products	Not applicable

Before you order, ask three things: which method measures size variants, which reference standard sets the mg, and which IU factor the report uses.

What published hGH results show

Finnrick’s public data summary, read on 4 October 2026, lists 18 hGH tests from 4 vendors, from 7 March to 14 September 2026. Seven passed and 11 failed under its default Purity Focus standard: HPLC purity of 99.5% or more and a dose within ±35% of the label. Its summary does not break failures down by reason.

The set is small, and the bar is strict for a protein: the pharmacopoeia’s related-proteins test allows up to 6.0% in the bulk active substance. Finnrick’s published standard covers purity and dose and has no dimer criterion. Read the COA behind a rating as well as the pass or fail.

One hGH group test of 21 to 22 members used two labs; our guide to running a group test covers the steps.

How to read an hGH COA

1. Molecule: somatropin, 191 amino acids. hGH fragment 176-191 is a different peptide.
2. Identity: expected and observed mass, or a peptide map against a reference.
3. Content: mg per vial, basis, reference standard, IU factor and % of label.
4. Purity: % area, the wavelength and the chromatogram.
5. Size variants, if ordered: dimer and larger aggregates as % of total, with the SEC chromatogram.
6. Safety tests, if ordered: endotoxin in EU per mg and per vial; sterility as the 14-day USP <71> test on its own unopened vials.
7. Batch and verification: the batch matches your vial, and the lab’s own site confirms the report.

What HK Analytical does for hGH

We do not offer hGH size-variant testing (SEC), and hGH is not on our list of compounds. For a compound that is not listed, you can ask in a quote request. For the peptides we test, one order can combine identity (LC-MS), purity (HPLC), content per vial, endotoxin (LAL), Sterility (USP <71>, 14 days) and our other tests. Results within days of receipt. Sterility (USP <71>, 14 days) is the one test that takes 14 days, because the method incubates for 14 days. Every number comes with its raw data, in a signed record you can check on /verify, as the example report shows.