Somatropin is recombinant human growth hormone — a 191-amino-acid single-chain protein with two intramolecular disulfide bridges, produced to match the sequence of the pituitary-derived hormone. Molecular formula C990H1528N262O300S7, molecular weight approximately 22,125 Da.
At roughly 22 kDa it is substantially larger than the short synthetic peptides that make up most of this catalogue, and it behaves differently as a result. Proteins of this size are more conformationally fragile than short sequences: biological activity depends on correct tertiary folding, not just on the amino acid sequence being intact.
Research context
The published literature examines growth hormone signalling through the GH receptor and the downstream JAK2/STAT5 pathway, hepatic IGF-1 production, and effects on protein, lipid and carbohydrate metabolism in model systems.
Because activity is conformation-dependent, analytical characterisation is a more involved question here than for a short peptide. A purity figure from reverse-phase HPLC speaks to chemical purity — it does not by itself establish that the protein is correctly folded. Researchers working with recombinant proteins typically supplement it with size-exclusion or bioassay data depending on what the work requires.
For a fuller treatment of the sequence, published models and technical data, see the HGH research guide.
Specification
CAS number 12629-01-5. Supplied as a white lyophilized powder at 24iu. This batch assayed at 99.51% purity, verified by HPLC and LC-MS at ILS Lab.
Handling
Handling matters more for a folded protein than for a short peptide. Reconstitute with bacteriostatic water, introducing the diluent slowly against the vial wall and swirling gently — never shake. Agitation and foaming denature proteins at this molecular weight, and the resulting loss of activity is not visible on inspection.
Store lyophilized at −20°C protected from light; refrigerate at 2–8°C once reconstituted and avoid repeated freeze-thaw cycles.
Ships with a batch-specific Certificate of Analysis. Cross-check the batch ID printed on your vial against the CoA before use — see the guide to reading a CoA if you are unfamiliar with the format.
Frequently asked questions about HGH
Why is HGH measured in iu rather than mg?
Because it is a folded protein whose activity depends on conformation, not merely on mass. International units express biological potency against a reference standard — which is the meaningful quantity for a protein that can be chemically intact but functionally inactive if misfolded. Short synthetic peptides are dosed by mass because sequence integrity and activity track closely; for a 22 kDa protein they do not.
Does a 99% purity figure mean the protein is active?
Not necessarily, and this is the key analytical point. Reverse-phase HPLC measures chemical purity — what proportion of the sample is the target molecule. It does not establish correct tertiary folding or intact disulfide bridges. A batch can assay at high purity and still have reduced biological activity. Researchers typically supplement with size-exclusion chromatography or bioassay data depending on what the work requires.
HGH or tesamorelin for growth hormone research?
Different approaches. HGH administers the hormone directly. Tesamorelin is a GHRH analogue that stimulates endogenous release from the pituitary, preserving the pulsatile secretion pattern and feedback regulation that direct administration bypasses. For modelling physiological signalling, the secretagogue is often the more appropriate tool; for work requiring defined exposure, the hormone itself.
Why does handling matter more for HGH?
Because denaturation is invisible. At 22 kDa, shaking and foaming disrupt tertiary structure, and the resulting loss of activity leaves no visual trace — the solution looks identical. Introduce diluent slowly against the vial wall, swirl rather than shake, avoid repeated freeze-thaw cycles, and never vortex.
Research use only. Not for human or veterinary use, not for use in diagnostic procedures, and not evaluated by the U.S. Food and Drug Administration.
