HGH 191AA

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What Is HGH 191AA?

HGH 191AA is recombinant human growth hormone (somatropin) in the 191-amino-acid native human sequence form. It is produced by recombinant DNA technology and matches the endogenous human GH polypeptide exactly — same 191 amino acids, same four-helix bundle three-dimensional structure, same two intramolecular disulfide bonds at Cys53–Cys165 and Cys182–Cys189. The 191AA designation specifically distinguishes the modern pharmaceutical-quality recombinant form from the older 192AA variant produced in bacterial expression systems, which carried an additional N-terminal methionine that introduced minor antigenicity differences and has been largely phased out of research and clinical use.

HGH is the principal peptide hormone secreted by somatotroph cells of the anterior pituitary in episodic pulses, with peak amplitudes occurring during early slow-wave sleep and following intense exercise. Endogenous secretion is regulated upstream by hypothalamic GHRH (positive) and somatostatin (negative). The recombinant 191AA form has empirical molecular weight 22,124 Da, INN somatropin, CAS number 12629-01-5 for the native protein and 96827-07-5 for the recombinant form. Standard unit activity for recombinant 191AA HGH is approximately 3 IU per mg according to the WHO International Standard. The compound is supplied as a high-purity lyophilized powder for reconstitution with bacteriostatic water. HGH is the most stringently regulated of all peptides in many jurisdictions and is approved for specific medical indications (paediatric GH deficiency, adult GH deficiency, Turner syndrome, idiopathic short stature, AIDS wasting, short bowel syndrome) only under prescription. The research-grade HGH 191AA sold here is supplied uitsluitend voor laboratoriumonderzoek and is not intended for human or veterinary administration. For peptides that stimulate endogenous GH release rather than supplying exogenous GH, see our Sermorelin, CJC-1295 met DAC, en Ipamorelin product pages.

Mechanism of Action — Growth Hormone Receptor Signalling and the GH/IGF Axis

What makes HGH 191AA mechanistically distinctive among research peptides is that it is the direct exogenous ligand for the growth hormone receptor — not an analog, not a secretagogue, but the native polypeptide itself. The downstream signalling cascade has been characterised across decades of published research:

• Growth hormone receptor (GHR) binding and homodimerisation — HGH binds a single GHR molecule with high affinity and induces homodimerisation with a second receptor unit, forming the bioactive 1:2 ligand-receptor complex. The dimerised receptor recruits cytoplasmic Janus kinase 2 (JAK2) to the intracellular receptor box motif, leading to trans-phosphorylation of JAK2 and the receptor itself. This is the canonical Type I cytokine-receptor activation mechanism.
• JAK2/STAT5 transcription factor activation — Phosphorylated JAK2 phosphorylates Signal Transducer and Activator of Transcription 5 (STAT5), primarily STAT5b, which then dimerises and translocates to the nucleus where it binds GH-responsive gene promoters. The dominant transcriptional output is induction of IGF-1 (Insulin-like Growth Factor 1) expression in hepatocytes — the principal endocrine effector of GH’s peripheral growth-promoting effects. Other GH-responsive genes include SOCS proteins (negative feedback), CIS, and a programme of liver-protein-synthesis genes.
• Direct and indirect (IGF-1-mediated) tissue effects — GH has two principal modes of action. Direct effects: lipolysis at adipocytes, glucose-counter-regulatory effects opposing insulin in muscle and liver, and direct anabolic signalling at GHR-expressing tissues including chondrocytes (in long-bone growth-plate research) and immune cells. Indirect effects via IGF-1: hepatic IGF-1 acts at the IGF-1 receptor on essentially every cell type to drive Akt/mTOR-mediated protein synthesis, cell proliferation, and survival signalling. The research compound IGF-1 LR3 is the canonical direct-IGF-receptor tool used to dissect direct GH effects from IGF-1-mediated downstream effects.

HGH has a relatively short plasma half-life (~3–5 hours following subcutaneous administration of the native protein) due to renal filtration and proteolytic clearance. The pulsatile pattern of endogenous secretion is a defining feature of the GH axis — tonic continuous exposure to GH produces different downstream gene-expression patterns than pulsatile exposure, an important consideration in research protocol design. Subcutaneous administration is the standard research route. For endogenous-pulse-pattern research, secretagogues like Sermorelin, CJC-1295, en Ipamorelin preserve the natural pulsatile signature; for direct GH-receptor pharmacology, exogenous HGH provides the cleaner stimulus.

Published Research Applications

HGH 191AA is used in laboratory research contexts that investigate:

• Growth hormone axis pharmacology — direct GHR signalling, JAK2/STAT5 phosphorylation kinetics, downstream IGF-1 induction; canonical research peptide for the GH side of the GH/IGF-1 axis
• IGF-1 induction research — hepatic IGF-1 gene expression, circulating IGF-1 dynamics, IGF-binding-protein (IGFBP) regulation; comparator for IGF-1 LR3-based research that bypasses the GH step
• Anabolic signalling research — skeletal-muscle protein synthesis via Akt/mTOR (largely IGF-1-mediated), bone-growth-plate chondrocyte signalling, adipose-tissue lipolysis
• Hepatic metabolism research — liver glucose output, lipid metabolism, hepatocyte-specific transcriptional response to GH stimulation
• GH-deficiency preclinical models — rescue studies in hypophysectomised rodents, Snell dwarf and Ames dwarf mouse models, transgenic GHR knockout characterisation
• Sleep and circadian research — relationship between sleep architecture and pulsatile GH secretion, slow-wave-sleep GH dependence
• Comparative GH-axis research — benchmarking against GHRH analogs (Sermorelin, CJC-1295) and growth hormone secretagogues (Ipamorelin, GHRP-6, GHRP-2) which produce endogenous GH pulses rather than exogenous GH replacement
• Tissue regeneration and wound healing research — published literature on GH effects in burn injury models, surgical recovery, and tissue regeneration; relationship to TB-500 en BPC-157 healing peptide research
• Endocrinology and aging research — somatopause and age-related GH decline, comparative studies of GH replacement vs GH-axis stimulation in aging research models.

For broader context on where HGH 191AA fits within the growth-axis peptide landscape, see Sermorelin en CJC-1295 met DAC as the GHRH-axis comparators, Ipamorelin as the selective GHS comparator, and IGF-1 LR3 as the downstream IGF-receptor agonist. Browse the full onderzoekspeptiden catalogus voor gerelateerde verbindingen.

Beschikbare sterktes en concentraties

MedsBase stocks HGH 191AA in five lyophilized vial sizes calibrated by international units (IU). Each strength is available in 10-vial or 20-vial pack formats with full reconstitution guidance:

All five strengths are the same chemical form (lyophilized recombinant 191AA somatropin, ≥98% HPLC purity). The IU labelling convention is the standard for HGH research and clinical literature; the approximate mg equivalents are provided for researchers calibrating dose against mg-based literature. Higher-IU vials require smaller reconstitution volumes per unit dose, useful for minimising injection volume in rodent protocols or running extended-cycle studies from a single vial.

How It Compares — HGH 191AA vs Sermorelin

HGH 191AA and Sermorelin represent the two opposing pharmacological approaches to GH-axis research: exogenous GH replacement vs endogenous GH stimulation. The comparison is one of the most-cited in growth-axis research design because the two approaches answer different research questions and produce qualitatively different downstream phenotypes.

For research interested in direct GHR pharmacology, IGF-1 induction kinetics, or replacing GH in deficiency models, HGH 191AA is the canonical research tool because it provides the exogenous ligand directly. For research interested in physiological pulsatile GH dynamics, hypothalamic-pituitary-axis pharmacology, or any protocol where preserving the natural somatostatin feedback loop matters, Sermorelin (and the related CJC-1295 met DAC) provide the upstream-stimulation alternative. Many published research designs use both in parallel arms to dissect direct GH effects from secretagogue-stimulated endogenous GH effects.

Opslag en Reconstituering

Voor reconstituering: store lyophilized vials refrigerated at 2–8 °C in original packaging for short-term working stock. For unopened long-term storage, freeze at −20 °C. Lyophilized recombinant HGH is stable under refrigeration for up to 24 months and at −20 °C for up to 36 months. The four-helix bundle folding state is preserved in the lyophilized form. Avoid freeze-thaw cycles on the lyophilized powder.

Reconstitueringsprocedure: inject bacteriostatic water down the side wall of the vial (not directly onto the lyophilized cake). Recommended reconstitution volumes vary by vial strength — for a 10 IU vial, 1.0 mL of bacteriostatic water yields a 10 IU/mL working concentration; for a 36 IU vial, 1.5 mL yields 24 IU/mL. Swirl gently — do niet shake — and allow 5–10 minutes for full dissolution. Recombinant proteins dissolve more slowly than small peptides; do not rush the dissolution step. Vigorous shaking can disrupt the four-helix bundle structure and reduce activity. A correctly reconstituted solution should be clear and colourless with no visible particles.

Na reconstitutie: store refrigerated at 2–8 °C and use within 14 days for optimal stability — somewhat shorter than the 30-day window for smaller synthetic peptides because the larger four-helix-bundle protein is more susceptible to surface adsorption losses and slow deamidation. Do not freeze the reconstituted solution — freeze-thaw cycles produce aggregation and loss of biological activity. Discard any vial showing cloudiness, precipitate, or discolouration. For long working dilutions below 0.1 mg/mL (~0.3 IU/mL), carrier protein (BSA at 0.1% final concentration) minimises adsorption losses.

Veelgestelde vragen

What is HGH 191AA used for in research?

HGH 191AA is used in laboratory research investigating direct growth hormone receptor pharmacology, JAK2/STAT5 signalling, hepatic IGF-1 induction, anabolic signalling in muscle and bone, hepatic metabolism, sleep-GH-axis relationships, GH-deficiency preclinical models, and comparative GH-axis pharmacology against GHRH analogs and growth hormone secretagogues. It is the canonical exogenous GH research tool. The research-grade HGH 191AA sold here is niet FDA-approved for non-clinical human use and is supplied strictly for laboratory research use only.

What is the difference between HGH 191AA and 192AA?

The 191AA form is the modern pharmaceutical-quality recombinant human growth hormone matching the exact native human sequence (191 amino acids). The 192AA form was an older bacterial-recombinant variant with an additional N-terminal methionine residue (192 amino acids total) that was used in early pharmaceutical development before mammalian-cell expression systems became standard. The extra methionine produced minor antigenicity in some patient populations and the 192AA form has been largely phased out of both research and clinical use. All research-grade HGH from MedsBase is the 191AA native-sequence form.

How is HGH 191AA different from Sermorelin?

HGH 191AA is exogenous growth hormone itself — the active receptor ligand. Sermorelin is a 29-amino-acid analog of GHRH (growth hormone releasing hormone) that stimulates the pituitary to release ENDOGENOUS GH. The downstream effects are similar in direction but qualitatively different: HGH produces tonic GHR exposure following each injection and bypasses pituitary feedback, while sermorelin produces a pulsatile GH release pattern and preserves natural somatostatin feedback regulation. Research designs typically use one or the other depending on whether the question is about direct GHR pharmacology (HGH) or hypothalamic-pituitary-axis dynamics (sermorelin).

How is HGH 191AA different from IGF-1 LR3?

HGH 191AA acts on the GH receptor, which drives IGF-1 production by the liver as the principal downstream effector. IGF-1 LR3 bypasses this step and acts directly on the IGF-1 receptor. Research using HGH studies the full GH/IGF-1 axis including the upstream liver-mediated IGF-1 induction; research using IGF-1 LR3 isolates the IGF-receptor pharmacology and the direct downstream Akt/mTOR anabolic signalling. Both compounds are frequently used in parallel arms of the same research design to dissect direct GH effects from IGF-1-mediated effects.

What is the typical HGH 191AA research dose?

Published preclinical research dose ranges are typically 1–8 IU per administration in rodent and primate models, given subcutaneously once daily or pulsed to mimic endogenous secretion patterns. A 10 IU vial reconstituted with 1.0 mL bacteriostatic water yields 10 IU/mL — 0.1 mL equals 1 IU, 0.2 mL equals 2 IU. The conversion factor is approximately 3 IU per mg of recombinant 191AA HGH (WHO international standard).

Is HGH 191AA FDA approved?

Pharmaceutical recombinant 191AA HGH (somatropin) is FDA-approved under multiple brand names (Genotropin, Humatrope, Norditropin, Saizen, Omnitrope, Nutropin and others) for specific medical indications including paediatric growth hormone deficiency, adult GH deficiency, Turner syndrome, idiopathic short stature, AIDS-associated wasting, and short bowel syndrome — only under prescription and supervision by an endocrinologist. The research-grade HGH 191AA sold here is a separate product supplied for laboratory research only and is niet FDA-approved for human or veterinary use. It is the most stringently regulated of all peptides in many jurisdictions.

How should HGH 191AA be stored?

Lyophilized vials: refrigerated at 2–8 °C for short-term working stock, or −20 °C for long-term storage of unopened vials. Reconstituted solution: refrigerated at 2–8 °C, use within 14 days (shorter than typical small peptides because the larger four-helix bundle is more susceptible to surface adsorption and slow deamidation). Do not freeze reconstituted solution — freeze-thaw cycles produce aggregation and loss of activity. Protect from direct light at all times.

How do I reconstitute HGH 191AA?

Follow the reconstitution procedure above. Add bacteriostatic water down the side wall of the vial (not onto the lyophilized cake), swirl gently, and allow 5–10 minutes for full dissolution. Do niet shake the vial — vigorous agitation can disrupt the four-helix bundle structure and reduce biological activity. A correctly reconstituted solution is clear and colourless with no visible particles.

Welke sterktes heeft MedsBase op voorraad?

MedsBase carries HGH 191AA in 10 IU, 15 IU, 24 IU, 36 IU, and 40 IU lyophilized vials. Each strength is available in 10-vial or 20-vial pack sizes. All vials are supplied at ≥98% HPLC purity with a certificate of analysis available on request.

Why is HGH measured in IU rather than mg?

International Units (IU) are the standard measurement for biological-activity-based labelling of protein hormones, established by the WHO International Standard. For recombinant 191AA HGH, the conversion factor is approximately 3 IU per mg. The IU labelling convention is preferred because it directly references biological potency rather than mass, which is more reproducible across different recombinant production batches that may vary slightly in glycosylation state, deamidation profile, and folding-state heterogeneity. Both IU and mg are valid; the IU is the dominant unit in clinical and research literature.

Why is the purity specification 98% rather than 99%?

Recombinant proteins like HGH cannot always achieve the ≥99% HPLC purity standard typical of small synthetic peptides because of inherent heterogeneity in any recombinant expression system — minor variants in folding state, deamidation isoforms, and other related species appear as related peaks on HPLC that are not impurities but isoforms of the target protein. ≥98% HPLC purity is a strong research-grade specification for recombinant 191AA HGH, intermediate between the 95% common for larger glycoproteins like Follistatin 344 and the 99% common for small synthetic peptides.

Does HGH 191AA cause side effects in research?

The principal on-target effects of HGH in research models are anabolic and metabolic: increased IGF-1 levels, increased lean body mass, decreased adiposity, transient insulin resistance, sodium and water retention, and increased mitogenic signalling. At supraphysiological exposures, off-target effects include carpal tunnel symptoms in primate models, glucose dysregulation, and (with chronic exposure) joint and soft-tissue overgrowth. The very strict regulatory framework around HGH for human use reflects these on-target risks at non-physiological doses.

What is the half-life of HGH 191AA?

In preclinical research, recombinant HGH has a plasma half-life of approximately 3–5 hours following subcutaneous administration. The relatively short half-life reflects renal filtration (a 22-kDa protein is at the boundary of the glomerular filtration cutoff) and proteolytic clearance. Tissue half-life is longer because GHR-bound HGH persists at the cell surface for some time before internalisation. For research protocols requiring sustained exposure, repeated daily dosing or specialised long-acting formulations would be needed; the standard recombinant 191AA form does not provide multi-day exposure from a single injection.

How long does HGH 191AA take to show effects in preclinical research?

Acute effects on JAK2/STAT5 phosphorylation and the immediate GH-responsive transcription programme are detectable within hours of administration. Hepatic IGF-1 induction peaks within 24 hours. Effects on body composition (lean mass, adipose mass) typically become statistically significant after 2–4 weeks of regular dosing in rodent models and continue to accrue through 8–12 weeks of continuous administration.

Can I order HGH 191AA for international shipping?

Yes, where local regulations permit. MedsBase ships HGH 191AA worldwide from our dedicated peptide shipping network. Peptide-only orders qualify for our standalone peptide shipping service. All orders ship in temperature-controlled packaging with full tracking and are covered by our Reshipment Assurance Policy. Note that HGH is the most stringently regulated peptide in many jurisdictions — please verify that local laws permit research-use-only acquisition in your destination country before ordering.

Other Peptides for Growth-Axis, GH-Release, and Anabolic Research

• Sermorelin — GHRH(1-29) analog — stimulates endogenous GH release
• CJC-1295 met DAC — Long-acting GHRH analog — canonical long-half-life GHRH research
• Ipamorelin — Selective growth hormone secretagogue — clean GH pulse without cortisol/prolactin
• IGF-1 LR3 — Long-arginine recombinant IGF-1 analog — bypasses the GH step
• GHRP-6 — First-generation hexapeptide GHS — ghrelin-axis GH release research

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