What is HGH somatropin? Identity, recombinant origin and verification
Somatropin is the International Nonproprietary Name for human growth hormone made with recombinant DNA technology (rhGH). In catalogs and in the lab it also appears as HGH somatropin, somatropin or rhGH. This guide covers only what the published literature says about the molecule: what it is, how it is made, how its identity is checked, and what being a protein means for lab handling. We do not cover clinical use.
The short answer
Recombinant human growth hormone is a 191-amino-acid protein of about 22 kDa, made in bacteria that carry the human gene and purified in several stages until its sequence and purity match what the pharmacopoeia requires. "Somatropin" is the name reserved for the version whose sequence is identical to the natural hormone. "HGH" is the general abbreviation. Because it is a large protein and not a short peptide, it is checked with more tests and handled with more care.
What somatropin is as a molecule
Somatropin is a 191-amino-acid protein weighing about 22 kDa (roughly 22,125 Da), held together by two disulfide bonds. Its sequence is identical to the growth hormone the pituitary makes naturally. By international convention, the name somatropin is reserved for preparations that replicate that sequence exactly.
Because it is a protein, somatropin does not behave like a short synthetic peptide. It is sensitive to heat, and over time slightly modified versions of the molecule can appear. Those variants show up as separate peaks in chromatography and are detectable by mass spectrometry.
Somatropin, pituitary hormone and somatrem
The three names are easy to mix up. The difference is in origin and sequence.
| Name | Origin | Sequence |
|---|---|---|
| Pituitary growth hormone | Made naturally by the pituitary | 191 amino acids |
| Somatropin (rhGH) | Recombinant, produced in E. coli | 191 amino acids, identical to the pituitary form |
| Somatrem (met-hGH) | Recombinant, from the first processes | 192: one extra methionine at the start of the chain |
So when a catalog says "somatropin", it is saying two things at once: the origin is recombinant, and the sequence matches the natural one. That second part is exactly what the identity test has to confirm.
How it is made: recombinant origin
Bacterial expression of human growth hormone was first described in 1979 by Goeddel and colleagues in Nature. They built a hybrid gene, part chemically synthesized DNA and part enzymatically prepared cDNA, and expressed it in Escherichia coli under the lac promoter, producing a polypeptide with the size and immunological properties of mature hGH. That work laid the technical groundwork for later industrial processes.
Today's commercial processes are variations on the same idea: grow E. coli carrying the inserted gene, extract the protein, purify it through several chromatography steps, and verify that the sequence and purity match what the pharmacopoeia requires.
How identity and purity are verified
Characterization of recombinant somatropin depends on a combination of physicochemical methods. For routine batch release, bioassays were replaced by objective analytical techniques. The usual axes are four.
Reversed-phase high-performance liquid chromatography (RP-HPLC). It separates the components in the batch and shows somatropin as a main peak. Variants modified by age or by the manufacturing process show up as neighboring peaks and are counted as product-related impurities. Our article on HPLC purity explains how to read that figure on a COA.
Peptide mapping after tryptic digestion. This is the identity test the pharmacopoeia requires. The protein is cut into fragments with an enzyme (trypsin), the resulting pattern is separated, and it is compared with the pattern from a reference standard. If the two patterns match, the sequence is what it should be.
Mass spectrometry (MS). Applied to the intact protein and to tryptic peptides, MS confirms the molecular mass, detects variants (methionine oxidation, asparagine or glutamine deamidation, truncated or aggregated species), and assigns each observed HPLC peak.
International reference standard. For potency readings and cross-laboratory calibration, the current reference material is the WHO Second International Standard for Somatropin, code NIBSC 98/574, established after an international collaborative study of 16 laboratories and reported by Bristow and Jespersen in 2001.
What a somatropin COA should show
A serious somatropin certificate of analysis (COA) names these techniques: HPLC for purity, MS for mass, tryptic mapping for sequence, and a quantitative comparison against the international standard or an in-house standard traceable to it. A document that only says "purity 99%" and nothing else is missing the tests that tell a correct protein from a similar one. Our article on how to read a peptide COA covers the rest of the document.
What this means for lab handling
Somatropin ships lyophilized. In dry form it is reasonably stable at refrigeration temperatures. In solution it is a mid-sized folded protein and therefore sensitive to temperature, mechanical agitation, UV light, freeze-thaw cycles and solvent quality. Our articles on peptide reconstitution and bacteriostatic vs. sterile water cover the general principles for lyophilized material, and the peptide calculator converts concentration to volume unambiguously. Storage conditions are in the storage guide.
From a purchasing point of view, what matters with any supplier is traceability: batch number, a COA with HPLC, MS and tryptic mapping, comparison against a traceable standard, and lot-to-lot consistency. HGH somatropin sits in the catalog of research peptides alongside incretin analogs and repair peptides.
Égida HGH
Égida HGH (somatropin) ships as a 12 IU lyophilized vial, research grade (RUO).
If you want to know the HGH somatropin cost for the 12 IU vial, the price is listed on the product page (from $480 MXN) and orders go through the cart. To compare suppliers, what to ask for before buying research HGH explains how to convert IU to milligrams and which tests to ask for in a protein COA.
Sources
- Goeddel DV, Heyneker HL, Hozumi T, et al. Direct expression in Escherichia coli of a DNA sequence coding for human growth hormone. Nature. 1979;281(5732):544–548. PMID: 386136.
- Bristow AF, Jespersen AM. The second international standard for somatropin (recombinant DNA-derived human growth hormone): preparation and calibration in an international collaborative study. Biologicals. 2001;29(2):97–106. PMID: 11580214.
- Bayol A, Bristow A, Charton E, Girard M, Jongen P. Somatropin and its variants: structural characterization and methods of analysis. Pharmeuropa Bio. 2004;2004(1):35–45. PMID: 15659284.