Description

HGH (191AA) – Advanced Biochemical Mechanism Profile

(Recombinant Human Growth Hormone – Somatotropin, 191 Amino Acids)

Recombinant HGH (191AA) is structurally identical to endogenous pituitary somatotropin. Its biological effects are mediated through the Growth Hormone Receptor (GHR), a class I cytokine receptor. Unlike GPCRs, GHR signals primarily via JAK2/STAT, MAPK, and PI3K/Akt pathways, leading to transcription of anabolic and metabolic genes.

---

✅ 1. Primary Receptor Target

Growth Hormone Receptor (GHR)

• Class: Cytokine receptor superfamily (not GPCR)

• Mechanism: Ligand-induced receptor dimerization

Mechanistic sequence:

1. HGH binds monomeric GHR

2. Receptor dimerizes

3. JAK2 (Janus kinase 2) autophosphorylates

4. JAK2 phosphorylates intracellular GHR tyrosines

5. Recruitment and activation of STAT transcription factors

---

✅ 2. Core Intracellular Signaling Cascades

A. JAK2 → STAT5 Pathway (Primary)

• STAT1/3/5 are phosphorylated

• Translocate to nucleus

• Bind GAS promoter elements

• Induce transcription of anabolic and metabolic genes

Key gene targets measured in research:

• IGF-1 (Insulin-like Growth Factor-1)

• ALS (Acid Labile Subunit)

• CIS/SOCS proteins (feedback regulators)

• STAT5-responsive muscle growth genes

---

B. PI3K → Akt / mTOR Pathway

• GHR → IRS-1/2 phosphorylation

• Recruitment of PI3K

• Activation of Akt, mTOR, p70S6K, 4E-BP1

• Supports protein synthesis and cellular growth processes

Gene targets:

• mTOR-regulated protein translation genes

• SREBP1 and metabolic regulators

• PGC-1α (metabolic coactivator)

---

C. Ras/Raf → ERK1/2 MAPK Pathway

• GHR recruits Shc/Grb2/SOS

• Activates Ras → Raf → MEK1/2 → ERK1/2

• Increases mitogenic gene transcription

MAPK-responsive genes:

• FOS, JUN, EGR1

• Cyclins involved in cell-cycle progression

---

✅ 3. IGF-1 Axis (Endocrine & Autocrine)

HGH induces hepatic and peripheral production of IGF-1, which then activates its own receptor (IGF-1R, a receptor tyrosine kinase).

IGF-1R signals via:

• IRS-1/2 → PI3K → Akt

• Ras/MAPK

• mTOR complex activation

Gene-level outputs:

• Myogenic regulatory factors (e.g., MYOD1, MYOG)

• COL1A1 and extracellular matrix remodeling genes

• Anti-apoptotic BCL2-family genes

---

✅ 4. Second Messengers & Enzymes Involved

---

✅ 5. Key Gene Targets Frequently Measured in Studies

---

✅ Receptor Kinetics

• Receptor dimerization-dependent activation

• Rapid STAT phosphorylation within minutes

• Secretion of IGF-1 provides prolonged downstream signaling

---

Research-Only Use Classification

HGH (191AA) is provided exclusively for in-vitro laboratory research.
It is not approved for human or animal administration, consumption, injection, or therapeutic or diagnostic use.