HGH is recombinant human growth hormone (somatropin), a 191-residue single-chain protein hormone corresponding to the mature product of the pituitary GH1 gene. It is a class I cytokine-family ligand, and in the laboratory it serves as the reference agonist for the growth hormone receptor (GHR) in binding assays, JAK2-STAT5 reporter systems and hepatocyte culture. NuVion supplies HGH as a laboratory chemical for in vitro research use only.
Key facts
| Type / class | Recombinant protein hormone, class I cytokine superfamily ligand |
| Amino acid count | 191 residues, single chain |
| Molecular weight | Approximately 22.1 kDa |
| CAS number | 12629-01-5 (somatropin) |
| Synonyms / other names | Somatropin, somatotropin, recombinant human growth hormone, rhGH, GH, 22K-GH |
| Supplied form | Lyophilised powder in a sealed vial |
Structure and chemistry
Growth hormone is a globular protein, far larger than the short synthetic peptides that share the same product category. The 191 residues fold into a four-helix bundle with up-up-down-down topology, the fold shared across the class I cytokines (prolactin, erythropoietin, interleukin-6). Two disulfide bridges constrain it: Cys53 to Cys165 closes a large loop across the core, and Cys182 to Cys189 closes a small loop near the C-terminus. Reduction of either bridge unfolds the bundle and abolishes receptor binding, so reducing agents are kept out of assay buffers.
Two surfaces on the molecule are functionally distinct. Site 1, the higher-affinity epitope, spans helix 4 and the connecting loop between helices 1 and 2. Site 2 sits on the opposite face on helices 1 and 3. Their sequential engagement is what makes the receptor complex a 1:2 assembly, and mutations at site 2 (the G120R substitution is the classic example) give proteins that occupy one receptor without recruiting a second, which is how antagonist tool proteins in this family were built.
The pituitary also produces a 20 kDa isoform, generated by alternative splicing that removes residues 32 to 46; the 22 kDa form described here is the predominant one and the form produced recombinantly. Recombinant material is expressed in bacterial or yeast systems and carries no glycosylation, matching the non-glycosylated native protein. Characteristic degradation routes are deamidation at asparagine residues in the flexible loops, oxidation of the two methionines, and non-covalent dimer and higher aggregate formation at air-water interfaces. Aggregation is the practical concern in handling: solutions are not shaken or vortexed vigorously, and carrier protein is often added to dilute working solutions to limit adsorption to labware.
Mechanism of action
GH signals through the growth hormone receptor, a single-pass transmembrane receptor with no intrinsic kinase activity. One GH molecule binds the extracellular domain of a first receptor through site 1, then recruits a second receptor through site 2, giving a 1:2 hormone:receptor complex. Receptor dimerisation brings the two intracellular tails together and repositions the JAK2 tyrosine kinase molecules held at the Box1 proline-rich motifs. JAK2 then trans-phosphorylates its partner’s activation loop, and the activated kinase phosphorylates tyrosines along the receptor tail.
The dominant downstream branch is STAT5b. Phosphotyrosines on the receptor and on JAK2 recruit STAT5b through its SH2 domain, JAK2 phosphorylates STAT5b at Tyr699, and phosphorylated STAT5b dimerises, enters the nucleus and binds gamma-interferon activated sequence (GAS) elements. Canonical STAT5b target genes include IGF1, IGFALS, SOCS2 and CISH. STAT1 and STAT3 are also phosphorylated, more weakly. Two further branches run in parallel: SHC recruitment feeding the RAS-RAF-MEK-ERK cascade, and IRS phosphorylation feeding PI3K and AKT. Signalling is terminated by the SOCS proteins, which are themselves STAT5b targets and which bind the receptor and JAK2 to form a negative feedback loop, and by the phosphatases PTP1B and SHP-1.
The IGF-1 axis is the second layer of this pathway and the reason GH is studied in hepatocyte models. STAT5b-driven transcription of IGF1 in hepatocytes raises secreted IGF-1, which circulates bound to IGFBP-3 and the acid-labile subunit encoded by IGFALS, and IGF-1 then acts on a separate receptor tyrosine kinase, IGF1R, with its own autophosphorylation and IRS-1/PI3K/AKT and ERK outputs. GHR signalling and IGF1R signalling are therefore experimentally separable, and separating them is a common design question in cell work using both a GH and an IGF-1 analogue. A proteolytic fragment of the receptor’s extracellular domain also circulates as growth hormone binding protein, which competes for free hormone in serum-containing media.
Research applications
HGH sits in the NuVion Growth Hormones category. Typical study contexts include:
- GHR binding assays on membrane preparations or receptor-expressing lines, and surface plasmon resonance measurement of site 1 and site 2 affinities.
- GAS-luciferase reporter assays in GHR-transfected HEK293 cells, giving a concentration-response curve for STAT5b transcriptional activity.
- Phospho-specific immunoblotting or phosphoflow for JAK2, STAT5b Tyr699, ERK1/2 and AKT, used to time the signalling cascade and to map SOCS-mediated feedback.
- Hepatocyte and HepG2 culture with qPCR or ELISA readout of IGF1, IGFALS and SOCS2 transcription, the standard cellular assay for the GH-IGF-1 axis.
- Proliferation bioassays in GH-responsive lines such as Nb2 cells, used historically to assign biological activity to a protein preparation.
- Analytical characterisation of a large protein: size-exclusion HPLC for aggregate content, RP-HPLC for purity, and intact or peptide-mapping mass spectrometry for identity and deamidation.
Handling in the laboratory
HGH is supplied as a lyophilised powder in a sealed vial. Reconstitution is with bacteriostatic water, added slowly down the vial wall and allowed to dissolve without shaking, since a folded protein at an air-water interface aggregates readily; the reconstitution calculator gives the volume needed for a target concentration. Keep the sealed vial dry, away from light and refrigerated as described in the product documentation. Keep the reconstituted solution refrigerated and use it within the period stated in the documentation, and aliquot it so that the stock is not subjected to repeated freeze-thaw cycles.
The protein is characterised by RP-HPLC for purity and by mass spectrometry for identity. A 22 kDa protein gives a multiply charged electrospray envelope, and the deconvoluted mass is compared against the calculated mass of the 191-residue chain with both disulfide bridges intact, which is 4 Da below the fully reduced mass.
Testing and supply from NuVion
NuVion has HGH independently tested by Janoshik Analytical. Most batches are tested, and the Certificate of Analysis for a tested batch, showing RP-HPLC purity and mass spectrometry identity, is published on the product page and in the Certificates of Analysis library. Manufacture is GMP-audited, material is supplied lyophilised in sealed vials, and orders are dispatched from within Australia.
Related compounds
In the same category, IGF-1 LR3 acts one step downstream at IGF1R and is used to separate the two arms of the axis, while Sermorelin acts one step upstream at the GHRH receptor on pituitary cells. The carboxy-terminal fragment studied on its own as AOD-9604, also catalogued as HGH fragment 176-191, is covered separately.
Frequently asked questions
What is HGH used for in research?
It is the reference agonist for the growth hormone receptor. Work with it includes GHR binding measurements, GAS-luciferase reporter assays, phospho-STAT5b immunoblotting, and hepatocyte culture where IGF1 and SOCS2 transcription are the readout for pathway activation.
How is HGH supplied?
As a lyophilised powder in a sealed vial, characterised by RP-HPLC purity and mass spectrometry identity. Because it is a folded 22 kDa protein, size-exclusion chromatography for aggregate content is also informative when assessing a preparation.
Is HGH a therapeutic good in Australia?
The material NuVion supplies is not included in the Australian Register of Therapeutic Goods and has not been assessed by the TGA. It is a laboratory chemical for in vitro research, and nothing on this page is a representation about therapeutic use.
How should HGH be stored?
Keep the sealed vial of lyophilised powder dry, away from light and refrigerated as stated in the product documentation. Keep the reconstituted solution refrigerated and use it within the period the documentation states. Aliquoting and gentle handling limit aggregation, which is the main way a protein preparation of this size loses activity.
Research use only. This product is a laboratory chemical supplied for in vitro research. It is not included in the Australian Register of Therapeutic Goods and has not been assessed by the Therapeutic Goods Administration for quality, safety or efficacy. It is not for human or veterinary use, and nothing on this page is a representation about therapeutic use.
