HGH

Recombinant Human Growth Hormone (HGH), also known as somatropin, is a recombinant 191-amino-acid protein with an amino acid sequence identical to endogenous human growth hormone produced by the anterior pituitary gland. Unlike growth hormone-releasing hormone (GHRH) analogues such as CJC-1295, recombinant HGH acts directly on the growth hormone receptor (GHR), making it an important research tool for investigating the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis, endocrine signalling, metabolism, skeletal biology, and protein synthesis.

Researchers within the European Union can buy HGH 10 IU from Crystal Peptides in a high-purity formulation for research use. To help verify the identity, purity, and quality of this recombinant research protein, every batch undergoes independent analytical testing by accredited laboratories. Batch-specific Certificates of Analysis provide researchers with documented information on product identity, purity, and analytical consistency, supporting confidence in the quality and traceability of the material supplied for laboratory research.

What’s the difference between HGH 10 IU vs HGH 36 IU?

The abbreviation IU in the description stands for International Unit, a standardised measurement of the biological activity of growth hormone. Both formulations contain the same recombinant human growth hormone protein and are manufactured to the same quality standards; the difference lies solely in the amount of biologically active growth hormone supplied per vial.

Researchers typically select the appropriate strength according to the objectives of the study, dosing strategy, and quantity of material required. A higher IU value does not indicate a different form of HGH or superior quality; it simply represents a greater quantity of biologically active recombinant growth hormone. International Units (IU) are widely used to standardise the biological activity of certain proteins, hormones, vitamins, and other biologically active substances, including insulin, heparin, erythropoietin, and vitamins A, D, and E. This standardised system allows researchers to compare biological activity consistently across different preparations regardless of manufacturer or formulation.

HGH (somatropin) properties and registry information

Note: HGH191AA is the full-length recombinant form of human growth hormone comprising 191 amino acids, matching the sequence of endogenous pituitary growth hormone. Unlike shorter growth hormone fragments or peptide derivatives, HGH191AA is a complete recombinant protein that directly activates the growth hormone receptor (GHR), making it the preferred research model for investigations into growth hormone signalling, endocrine physiology, metabolism, and insulin-like growth factor-1 (IGF-1) regulation.

Research background and published studies

Recombinant human growth hormone (HGH191AA) has one of the most extensively characterised evidence bases of proteins used in endocrine research. Because its amino acid sequence is identical to endogenous human growth hormone, decades of biochemical, physiological, and clinical investigations have established a detailed understanding of its molecular structure, receptor interactions, and biological functions.

The studies summarised below are intended to explain the scientific background of recombinant HGH and should not be interpreted as evidence of clinical efficacy or therapeutic use of this research material.

Discovery of recombinant human growth hormone

Growth hormone was first isolated from the human pituitary gland during the mid-twentieth century, providing researchers with an important tool for investigating endocrine physiology and somatic growth. The development of recombinant DNA technology in the 1980s transformed the field by enabling production of full-length recombinant human growth hormone (somatropin) with an amino acid sequence identical to the endogenous hormone. Recombinant HGH191AA subsequently became the standard research model for investigating growth hormone biology, replacing pituitary-derived preparations and allowing more consistent biochemical and physiological investigations.

Growth hormone receptor signalling

Human growth hormone exerts its biological activity by binding to the growth hormone receptor (GHR), a transmembrane receptor expressed in numerous tissues throughout the body. Receptor activation promotes dimerisation of the GHR and initiates intracellular signalling through pathways including Janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5). These signalling cascades regulate the expression of numerous genes involved in growth, metabolism, cellular differentiation, and endocrine function, making recombinant HGH an important research tool for investigating receptor pharmacology and downstream signalling mechanisms. [1]

The growth hormone/IGF-1 axis

One of the principal physiological actions of growth hormone is stimulation of insulin-like growth factor-1 (IGF-1) production, particularly within the liver. The GH/IGF-1 axis plays a central role in regulating skeletal growth, protein metabolism, tissue maintenance, and endocrine homeostasis. Because recombinant HGH directly activates the growth hormone receptor while preserving this downstream endocrine cascade, researchers frequently use it to investigate interactions between growth hormone signalling, IGF-1 production, receptor regulation, and hormonal feedback mechanisms. [2]

Current scientific understanding

Unlike growth hormone secretagogues such as CJC-1295, which stimulate endogenous growth hormone release through activation of the growth hormone-releasing hormone receptor (GHRHR), recombinant HGH acts directly at the growth hormone receptor itself. This distinction has made HGH191AA a valuable reference compound in endocrine research, allowing investigators to differentiate the biological effects of direct receptor activation from those resulting from stimulation of endogenous hormone secretion. The observations described above are derived from decades of published endocrine and molecular research and are presented solely to summarise the scientific literature relevant to recombinant human growth hormone.

HGH mechanism of action

Recombinant human growth hormone (HGH191AA) has a well-characterised mechanism of action established through decades of biochemical, molecular, and endocrine research. As a full-length recombinant protein identical to endogenous human growth hormone, HGH binds directly to the growth hormone receptor (GHR), initiating a series of intracellular signalling pathways that regulate growth, metabolism, and endocrine function.

Direct growth hormone receptor activation

The growth hormone receptor is expressed in numerous tissues throughout the body, including the liver, skeletal muscle, bone, adipose tissue, and other metabolically active organs. Binding of recombinant HGH to the extracellular domain of the receptor induces receptor dimerisation, an essential step that initiates intracellular signal transduction. [1]

Unlike growth hormone secretagogues such as CJC-1295, which stimulate endogenous hormone release from the anterior pituitary, recombinant HGH bypasses hypothalamic-pituitary regulation by acting directly at the growth hormone receptor.

JAK2/STAT5 signalling

Activation of the growth hormone receptor rapidly recruits and activates Janus kinase 2 (JAK2), leading to phosphorylation of signal transducer and activator of transcription 5 (STAT5) and several additional intracellular signalling proteins. The JAK2/STAT5 pathway regulates transcription of genes involved in cellular growth, protein synthesis, metabolism, and endocrine function, while complementary pathways including MAPK/ERK and PI3K/Akt contribute to the broader biological effects associated with growth hormone signalling. Because these signalling networks are well characterised, recombinant HGH has become an important reference protein for studying receptor pharmacology and intracellular signal transduction. [1,3]

The GH/IGF-1 axis

One of the principal downstream effects of growth hormone receptor activation is stimulation of insulin-like growth factor-1 (IGF-1) synthesis, particularly within the liver. The resulting GH/IGF-1 axis regulates numerous physiological processes, including skeletal growth, protein turnover, tissue maintenance, and metabolic homeostasis. Recombinant HGH therefore provides researchers with a direct means of investigating endocrine regulation across the entire growth hormone signalling cascade, from receptor activation through to downstream IGF-1 production and feedback mechanisms. [2]

Current scientific understanding

The biological activity of recombinant HGH is among the best characterised of any protein used in endocrine research. Its molecular structure, receptor interactions, intracellular signalling pathways, and physiological effects have been investigated extensively over several decades.

Consequently, recombinant HGH191AA continues to serve as a reference standard for studies of growth hormone receptor biology, endocrine signalling, and the regulation of the GH/IGF-1 axis. Despite this abundance of research, the mechanisms described above are presented solely to summarise the current scientific literature and should not be interpreted as evidence of clinical efficacy or authorised therapeutic use of this research material.

Recombinant HGH research applications

Because recombinant HGH191AA is structurally identical to endogenous human growth hormone, it has become one of the most widely used research proteins in endocrinology. Researchers use it to investigate how growth hormone influences growth, metabolism, tissue maintenance, and endocrine regulation under controlled laboratory conditions.

The applications described below are based on published scientific research and are presented solely to summarise the current understanding of recombinant human growth hormone. They should not be interpreted as evidence of clinical efficacy or authorised therapeutic use.

Growth hormone and endocrine research

Recombinant HGH is used extensively to investigate the biology of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis. Researchers can use it to study how growth hormone regulates endocrine signalling, interacts with the pituitary and liver, influences circulating IGF-1 concentrations, and participates in the complex feedback mechanisms that maintain hormonal balance. Because recombinant HGH acts directly at the growth hormone receptor, it provides a well-characterised model for studying endocrine physiology without relying on endogenous hormone release.

Metabolism and body composition

Growth hormone has long been investigated for its role in regulating protein, carbohydrate, and lipid metabolism. Experimental studies have explored how HGH influences nutrient utilisation, energy expenditure, body composition, and protein turnover at both the cellular and whole-organism level. These investigations contribute to a broader understanding of metabolic regulation and the biological functions of the GH/IGF-1 axis.

Bone, muscle, and connective tissue biology

Another major area of research concerns the role of growth hormone in musculoskeletal biology. Published studies have investigated how HGH interacts with bone remodelling, skeletal development, muscle physiology, collagen metabolism, and connective tissue maintenance. Because these processes are closely linked to growth hormone signalling, recombinant HGH is frequently used to examine the molecular pathways that regulate tissue growth and maintenance.

Comparative endocrine studies

Recombinant HGH is also widely used as a reference protein when comparing different approaches to growth hormone research. While HGH activates the growth hormone receptor directly, compounds such as CJC-1295 with DAC and Modified GRF (1-29) stimulate the body's own release of endogenous growth hormone through the growth hormone-releasing hormone receptor. Comparing these approaches enables researchers to distinguish the effects of direct receptor activation from those associated with physiological growth hormone secretion and endocrine feedback.

Current areas of investigation

Contemporary research continues to use recombinant HGH to investigate endocrine physiology, receptor pharmacology, healthy ageing, metabolism, skeletal biology, and the regulation of the GH/IGF-1 axis. Although the scientific literature describing human growth hormone is extensive, Crystal Peptides supplies recombinant HGH exclusively as a laboratory research reagent. The product is intended solely for research and development and is not authorised for human or veterinary use.

Recombinant HGH compared to related endocrine research compounds

Recombinant HGH belongs to a broader group of research compounds used to investigate the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis. Although these compounds are often discussed together, they act at different points within the endocrine signalling pathway and are therefore used to answer different scientific questions. Understanding these distinctions helps researchers select the most appropriate model for their experimental objectives.

Recombinant HGH vs CJC-1295 with DAC

Although both compounds are used to investigate growth hormone biology, they act at different stages of the endocrine signalling pathway. Recombinant HGH binds directly to the growth hormone receptor, allowing researchers to study the biological effects of growth hormone itself. On the other hand, CJC-1295 with DAC stimulates the pituitary gland to release endogenous growth hormone through activation of the growth hormone-releasing hormone receptor. Its Drug Affinity Complex extends circulation time through albumin binding, making it well suited to studies of prolonged endogenous growth hormone stimulation.

Recombinant HGH vs IGF-1 LR3

While recombinant HGH and IGF-1 LR3 are closely related within the same endocrine pathway, they are not interchangeable. HGH acts at the beginning of the cascade by activating the growth hormone receptor, which subsequently stimulates endogenous production of insulin-like growth factor-1. IGF-1 LR3 bypasses this upstream regulation by acting directly at the IGF-1 receptor. Comparing these compounds allows researchers to distinguish between biological responses mediated by growth hormone itself and those resulting from downstream IGF-1 signalling.

Quality and testing

Crystal Peptides is committed to supplying recombinant HGH that meets high standards of analytical quality, consistency, and traceability needed for laboratory research in growth hormone signalling. Every batch of recombinant human growth hormone undergoes independent analytical testing by accredited laboratories, including Janoshik, and is supported by a batch-specific Certificate of Analysis (COA), allowing researchers to verify the identity, purity, and quality of the material before incorporating it into experimental work.

Quality testing of recombinant HGH

Because recombinant human growth hormone is a full-length protein and not a short synthetic peptide, quality assessment extends beyond normal measures of purity. Researchers should evaluate multiple analytical parameters to confirm that the protein has been correctly manufactured, characterised, and handled throughout the production process.

Analytical assessment may include:

• High-performance liquid chromatography (HPLC) to evaluate chromatographic purity and detect potential impurities or degradation products.
• Mass spectrometry (LC-MS) to verify the molecular identity of recombinant human growth hormone and confirm the expected molecular mass.
• Protein identity testing, confirming that the supplied material corresponds to full-length recombinant HGH191AA.
• Endotoxin testing, helping verify that endotoxin concentrations remain within appropriate limits for laboratory research.
• Sterility testing, providing additional assurance regarding microbiological quality during manufacture and packaging.
• Batch-specific Certificates of Analysis (COAs) documenting analytical methods, purity results, and independent laboratory verification for the exact batch supplied.

Considering these analytical results together provides a more complete assessment of product quality than relying on a reported purity percentage alone. Independent verification enables researchers to evaluate the identity, integrity, consistency, and traceability of recombinant HGH before use in experimental protocols.

Reconstitution and storage

Recombinant HGH is supplied as a lyophilised protein and is typically reconstituted in laboratory settings using sterile water or bacteriostatic water. The diluent should be introduced slowly down the inside wall of the vial to minimise foaming and mechanical stress on the protein. Following reconstitution, the solution should be mixed gently rather than shaken vigorously, as excessive agitation may contribute to protein denaturation or aggregation.

Lyophilised HGH should be stored at -20°C or below, protected from light and moisture until required for research. Once reconstituted, solutions should be refrigerated at 2–8°C, handled using appropriate laboratory procedures, and protected from repeated freeze-thaw cycles to help preserve protein stability and biological integrity.

Regulatory and legal

All products supplied by Crystal Peptides are intended exclusively for research and development purposes. Recombinant HGH191AA is supplied solely as a laboratory research protein for use by qualified professionals in controlled scientific settings and is not intended for human or veterinary use.

Although recombinant human growth hormone (somatropin) is the active ingredient used in a number of authorised medicinal products, the HGH supplied by Crystal Peptides is not an authorised medicine and must not be regarded as equivalent to any licensed pharmaceutical product. It is supplied exclusively as a research reagent for laboratory investigation, and any references to published endocrine or clinical research are provided solely to explain the biology, pharmacology, and scientific background of recombinant human growth hormone.

This product is not a medicinal product, food, food supplement, medical device, or cosmetic. It has not been evaluated or authorised by the European Medicines Agency (EMA), the U.S. Food and Drug Administration (FDA), or any other medicines regulator for clinical use in the form supplied by Crystal Peptides. The information presented on this page has not been evaluated by any regulatory authority and should not be interpreted as evidence of clinical efficacy or as a recommendation for therapeutic use.

Researchers and purchasers are responsible for ensuring that the acquisition, importation, storage, handling, use, and disposal of recombinant HGH comply with all applicable national and local laws and regulations. Because legislation governing research materials varies between jurisdictions, customers should verify the legal requirements applicable within their own country before purchasing or importing laboratory reagents.

Scientific References

• Dehkhoda F, Lee CMM, Medina J, Brooks AJ. The Growth Hormone Receptor: Mechanism of Receptor Activation, Cell Signaling, and Physiological Aspects. Front Endocrinol (Lausanne). 2018 Feb 13;9:35. doi:10.3389/fendo.2018.00035.
• Yuen KCJ, Hjortebjerg R, Ganeshalingam AA, Clemmons DR, Frystyk J. Growth hormone/insulin-like growth factor I axis in health and disease states: an update on the role of intra-portal insulin. Front Endocrinol (Lausanne). 2024 Nov 21;15:1456195. doi:10.3389/fendo.2024.1456195.
• Tian M, Qi Y, Zhang X, Wu Z, Chen J, Chen F, Guan W, Zhang S. Regulation of the JAK2-STAT5 Pathway by Signaling Molecules in the Mammary Gland. Front Cell Dev Biol. 2020 Nov 17;8:604896. doi:10.3389/fcell.2020.604896.

Frequently Asked Questions

Is HGH the same as somatropin?

Yes. Somatropin is the International Nonproprietary Name (INN) for recombinant human growth hormone, while HGH (Human Growth Hormone) is the more commonly used name in scientific literature and the research market. Both terms describe the same full-length 191-amino-acid recombinant protein with an amino acid sequence identical to endogenous human growth hormone. The HGH supplied by Crystal Peptides is recombinant somatropin provided exclusively for laboratory research.

Is HGH a peptide?

Strictly speaking, no. Although growth hormone is composed of amino acids like peptides, recombinant HGH is more accurately classified as a protein hormone because it consists of 191 amino acids, making it substantially larger than the short synthetic peptides commonly used in laboratory research. This distinction is important because recombinant HGH possesses a well-characterised three-dimensional protein structure and directly activates the growth hormone receptor, whereas many research peptides are considerably shorter and often act through different biological mechanisms.

Is the HGH supplied by Crystal Peptides a licensed pharmaceutical product?

No. Although somatropin is the active ingredient used in a number of authorised medicinal products, the recombinant HGH supplied by Crystal Peptides is not an authorised medicine. It is manufactured and supplied exclusively as a laboratory research protein for research and development purposes and is not intended for human or veterinary use. Any references to published clinical or endocrine research are provided solely to explain the biology and pharmacology of recombinant human growth hormone.

Is this full-length recombinant HGH191AA?

Yes; as indicated on the product, Crystal Peptides supplies HGH191AA, the full-length recombinant form of human growth hormone comprising 191 amino acids. Its amino acid sequence is identical to endogenous human growth hormone produced by the anterior pituitary gland, making it an important reference protein for investigating growth hormone receptor signalling, endocrine physiology, and the GH/IGF-1 axis in laboratory research.

What is the difference between HGH191AA and HGH fragments?

HGH191AA is the complete 191-amino-acid recombinant human growth hormone protein and directly activates the growth hormone receptor (GHR). By contrast, HGH fragments are shorter portions of the parent protein, such as HGH 176-191, that have been developed to investigate specific biological processes rather than the full range of growth hormone activity. Because they differ substantially in structure, receptor interactions, and research applications, HGH191AA and HGH fragments should not be regarded as interchangeable research compounds.

How can I verify the quality of recombinant HGH before buying?

Researchers should evaluate several indicators of quality rather than relying on purity claims alone. Important considerations include independent third-party analytical testing, batch-specific Certificates of Analysis, confirmation that the material is full-length HGH191AA, and analytical verification of protein identity and purity using techniques such as HPLC and LC-MS. Purchasing from a supplier that provides transparent analytical documentation and batch traceability allows researchers to independently assess the identity, quality, and consistency of the recombinant protein before incorporating it into laboratory studies.

Does Crystal Peptides provide third-party testing and a Certificate of Analysis (COA)?

Like every research compound we sell, recombinant HGH supplied by Crystal Peptides undergoes independent analytical testing by accredited laboratories and is supported by a Certificate of Analysis. The COA provides researchers with documented information relating to protein identity, analytical purity, and quality verification, allowing the exact batch supplied to be reviewed before use in laboratory research.

How is recombinant HGH tested?

Recombinant HGH should be evaluated using multiple analytical techniques to verify its identity, purity, and overall quality. Common methods include high-performance liquid chromatography (HPLC) to assess chromatographic purity, liquid chromatography-mass spectrometry (LC-MS) to confirm protein identity and molecular mass, together with sterility and endotoxin testing where appropriate for recombinant proteins intended for laboratory research. Reviewing these analytical results alongside a batch-specific Certificate of Analysis provides researchers with a more complete assessment of product quality and consistency.

Can recombinant HGH be reconstituted with bacteriostatic water?

In laboratory settings, recombinant HGH is commonly reconstituted using either bacteriostatic water or sterile water, depending on the experimental protocol. The diluent should be introduced slowly down the inside wall of the vial to minimise foaming, after which the solution should be mixed gently rather than shaken vigorously to help preserve protein integrity. Researchers should always follow their laboratory's standard operating procedures and the storage guidance provided with the product.

How should recombinant HGH be stored after reconstitution?

Following reconstitution, recombinant HGH should typically be stored under refrigeration at 2–8°C and protected from repeated freeze-thaw cycles, excessive agitation, and prolonged exposure to elevated temperatures. Lyophilised material should be stored at -20°C or below until required for research. Appropriate storage and handling practices help preserve protein stability and analytical integrity throughout the course of laboratory investigations.

How do I choose between 10 IU and 36 IU HGH?

Both the 10 IU and 36 IU formulations supplied by Crystal Peptides contain the same full-length recombinant HGH191AA protein and are manufactured to the same analytical quality standards. The difference lies only in the amount of biologically active growth hormone supplied per vial, expressed as International Units (IU). Researchers typically select the appropriate strength according to the objectives of the study, anticipated dosing strategy, and the quantity of material required. A higher IU value does not indicate a different formulation or superior quality.

Why choose recombinant HGH instead of a growth hormone secretagogue?

The choice depends on the objectives of the research. Recombinant HGH directly activates the growth hormone receptor (GHR), allowing researchers to investigate the biological effects of growth hormone itself. Growth hormone secretagogues, including compounds such as CJC-1295 and Ipamorelin, stimulate the body's own release of endogenous growth hormone through upstream endocrine pathways. Comparing these different approaches enables researchers to distinguish direct receptor activation from physiological hormone secretion and provides complementary models for investigating the GH/IGF-1 axis.

Where can I buy HGH for research purposes in Europe?

Researchers within the European Union can buy HGH 10 IU for research purposes directly from Crystal Peptides in high-purity 10 IU and 36 IU formulations. HGH supplied by Crystal Peptides is provided exclusively for laboratory research and development and is not intended for human or veterinary use.

Does Crystal Peptides ship recombinant HGH across Europe?

Crystal Peptides supplies recombinant HGH throughout Europe and ships using discreet packaging and tracked delivery services. Information regarding shipping destinations, estimated delivery times, payment methods, and ordering procedures is available on the Shipping Information page and in the Crystal Peptides FAQ.