Side-by-side · Research reference

HGH 191AAvsMGF

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AFDA-ApprovedHUMAN-REVIEWED0/75 cited

BAnimal-StrongHUMAN-REVIEWED14/55 cited

HGH 191AA

Recombinant hGH · FDA-Approved

0.024–0.034 mg/kg/dayPediatric GHD dose

2–4 hoursPlasma half-life

191 AASequence length

SQ · Daily · Evening preferred

MGF

IGF-1Ec Splice Variant · Muscle-Specific

IGF-1EcSplice variantArmakolas 2016

24-AASynthetic E-domain

Animal onlyHuman evidence

SQ · Research context only

01Mechanism of Action

Parameter

HGH 191AA

MGF

Primary target

Growth hormone receptor (GHR) — JAK2/STAT5 pathway

Satellite cells (Pax7+) in skeletal muscleMoore 2018

Pathway

GHR activation → JAK2/STAT5 → liver IGF-1 synthesis + direct metabolic effects

Mechanical stress → IGF-1Ec mRNA upregulation → Local E-domain peptide release → Satellite cell activation

Downstream effect

Linear growth, lipolysis, protein synthesis, nitrogen retention, carbohydrate metabolism modulation

Satellite cell proliferation, myoblast differentiation, muscle fiber repair

Feedback intact?

No — exogenous GH bypasses hypothalamic-pituitary axis, suppresses endogenous pulsatility

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Origin

Recombinant DNA technology — 191 AA, identical to pituitary hGH, no methionyl residue

Alternative splicing of IGF-1 gene (exons 4-6) produces IGF-1Ec precursor; E-domain cleaved post-translationallyArmakolas 2016 Vassilakos 2017

Antibody development

Rare — <2% develop binding antibodies, typically non-neutralizing

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02Dosage Protocols

Parameter

HGH 191AA

MGF

Pediatric GHD

0.024–0.034 mg/kg/day SQ

6–7× per week dosing typical. Brand-specific ranges.

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Adult GHD

0.004–0.016 mg/kg/day SQ

Start low, titrate based on IGF-1 levels.

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Turner syndrome

0.045–0.050 mg/kg/day SQ

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Idiopathic short stature

0.037 mg/kg/day SQ

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AIDS wasting

0.1 mg/kg/day SQ (high-dose)

Short-term indication. Monitor glucose.

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Frequency

Once daily, typically evening

Evening administration mimics physiological GH pulse.

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Evidence basis

FDA-approved / decades of RCT data

Animal models + in vitro only

Monitoring

IGF-1, glucose, thyroid function, bone age (children)

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Duration

Years (children until epiphyseal closure); indefinite (adult GHD)

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Synthetic peptide

—

24-amino-acid E-domain sequence

Corresponds to human IGF-1Ec exons 4-6 region.

Rodent cardiac model

—

200 μg/kg via peptide-eluting microstructures

Post-MI injection; improved ejection fraction by 8 weeks.

Acute delivery (mouse MI)

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Single bolus within 12 hrs post-infarctionShioura 2014

Delayed decompensation; no human protocol established.

Human evidence

—

None — no published clinical trials

All dosing extrapolated from animal models.

Detection in doping

—

Full-length MGF detected via LC-MS in illicit productsThevis 2014

WADA-prohibited since 2005; no therapeutic indication.

03Metabolic / Fat Loss Evidence

Parameter

HGH 191AA

MGF

Primary fat target

Visceral and subcutaneous adipose tissue

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Mechanism

Lipolysis via hormone-sensitive lipase activation, FFA oxidation

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Effect on lean mass

Significant lean mass increase (protein synthesis, nitrogen retention)

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Insulin sensitivity

Acute insulin resistance (anti-insulin effect); chronic neutral-to-improved via fat loss

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IGF-1 elevation

Dose-dependent, significant — primary anabolic mediator

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Glucose metabolism

Hyperglycemia risk, especially high doses (AIDS wasting)

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Body composition

↓ fat mass, ↑ lean mass, ↑ bone mineral density (children)

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Clinical context

FDA-approved for AIDS wasting (cachexia). Off-label use for body recomposition lacks long-term safety data.

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04Side Effects & Safety

Parameter

HGH 191AA

MGF

Injection site reaction

Lipohypertrophy, lipoatrophy, erythema (rotate sites)

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Fluid retention / Edema

Peripheral edema, arthralgia, carpal tunnel syndrome (dose-dependent)

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Glucose intolerance

Hyperglycemia, new-onset diabetes (anti-insulin effect)

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Intracranial hypertension

Benign intracranial hypertension (pseudotumor cerebri) — headache, visual changes, papilledema

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Slipped capital femoral epiphysis

SCFE risk in children — limp, hip/knee pain (requires surgery)

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Scoliosis progression

Rapid growth may unmask/progress scoliosis (monitor spine in children)

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Hypothyroidism

Central hypothyroidism unmasking or worsening (monitor TSH, free T4)

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Cancer risk

Contraindicated in active malignancy. Theoretical risk in cancer survivors (controversial).

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Antibody formation

Rare (<2%), typically non-neutralizing. Loss of efficacy if neutralizing antibodies develop.

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Pancreatitis

Rare. Higher risk in children with certain syndromes (Prader-Willi).

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Gynecomastia

Adolescent males (physiological during puberty, may be exacerbated)

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Human safety data

—

None — no clinical trials published

Theoretical IGF-1 axis risk

—

Chronic IGF-1Ec overexpression linked to cancer progression (prostate, colorectal, breast)

Tumor promotion

—

IGF-1Ec overexpressed in osteosarcoma, colorectal polyps with dysplasia, endometrial cancer

Antibody development

—

Unknown — no longitudinal human exposure data

Local injection reaction

—

Presumed similar to other peptides (erythema, induration) — no direct evidence

Dysregulated expression with age

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Older adults (70+ yrs) show blunted IGF-1Ec response post-exercise vs youngMoore 2018

Absolute Contraindications

HGH 191AA

·Active malignancy or history of cancer (especially childhood cancer survivors with risk factors)
·Acute critical illness (post-cardiac surgery, trauma, acute respiratory failure)
·Diabetic retinopathy (active proliferative or severe non-proliferative)
·Prader-Willi syndrome with severe obesity, sleep apnea, or respiratory impairment
·Closed epiphyses (for growth indications)

MGF

·Active malignancy or history of IGF-1-sensitive cancers (prostate, colorectal, breast, osteosarcoma)
·No established therapeutic use — investigational only

Relative Contraindications

HGH 191AA

·Diabetes mellitus (monitor closely, may require insulin adjustment)
·Intracranial lesions or history of intracranial hypertension
·Scoliosis (monitor curve progression)
·Untreated hypothyroidism (treat before GH initiation)
·Severe obesity (assess OSA risk, cardiovascular status)

MGF

·Family history of IGF-1-axis malignancies
·Use outside research setting

05Administration Protocol

Parameter

HGH 191AA

MGF

1. Reconstitution (if lyophilized)

Add diluent (sterile water or bacteriostatic water per manufacturer) to vial. Swirl gently — do not shake. Solution should be clear, colorless. Concentration varies by brand (e.g., 5 mg or 10 mg per vial).

MGF (E-domain peptide) has no approved clinical protocol. All published data derive from animal models or in vitro experiments.

2. Injection site

Subcutaneous — rotate sites: abdomen, thigh, buttocks, upper arm. Avoid same site within 1 cm for 2 weeks to prevent lipodystrophy.

Commercially available MGF corresponds to the 24-amino-acid human E-domain (hEc). Rodent E-domain (Eb) is structurally distinct and not interchangeable.

3. Timing

Once daily, evening preferred (6–8 PM or pre-sleep). Mimics physiological nocturnal GH secretion. Consistency is critical.

Rodent studies used peptide-eluting polymeric microstructures (cardiac) or direct intramuscular injection. Routes and doses non-translatable to humans.Peña 2015 Shioura 2014

4. Storage

Unreconstituted: refrigerate 2–8 °C, protect from light. Reconstituted: refrigerate, use within 14–28 days (brand-specific). Do not freeze.

MGF peptides prohibited in sport since 2005. Detection via LC-MS established for full-length MGF products.Thevis 2014

5. Needle

27–31G, 4–8 mm insulin syringe or pen device. Pinch skin, 45–90° angle depending on subcutaneous thickness.

Any human use falls outside approved medical practice and regulatory frameworks. No safety or efficacy data exist.

6. Monitoring

Baseline and periodic: IGF-1 (target age/sex-adjusted midrange), fasting glucose, HbA1c, thyroid function (TSH, free T4), bone age (children), lipid panel. Fundoscopy if headache/visual symptoms.

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06Stack Synergy

HGH 191AA

+ Ipamorelin

Moderate

View Ipamorelin →

Ipamorelin (GHRP) stimulates endogenous GH release, which is redundant when exogenous rhGH is administered. However, ipamorelin may still amplify pulsatility of remaining endogenous secretion in partial GHD or during GH dose titration. Not typically combined in standard clinical practice; more common in experimental or off-label protocols. Limited evidence for additive benefit.

HGH 191AA: Standard dose per indication
Ipamorelin: 100–200 mcg SQ · morning (if used)
Note: Monitor IGF-1 closely; avoid supraphysiological levels
Primary benefit: Theoretical enhancement of pulsatility; limited clinical rationale

+ Tesamorelin

Weak

View Tesamorelin →

Tesamorelin (GHRH analogue) stimulates endogenous GH secretion, which is unnecessary when exogenous rhGH is already provided. Combining both offers no mechanistic advantage and increases cost, side effects, and IGF-1 elevation risk. Not recommended in clinical practice.

Note: Combination not recommended — choose one GH modality
Primary benefit: None — redundant mechanisms

MGF

+ BPC-157

Multi-pathway

View BPC-157 →

MGF activates satellite cells for muscle fiber repair; BPC-157 promotes angiogenesis, collagen synthesis, and tendon healing via distinct pathways (VEGF, FAK, integrin signaling). Theoretical synergy in post-injury contexts combines myogenic (MGF) and stromal (BPC-157) repair mechanisms. Both lack human validation.

MGF: No established dose
BPC-157: 250–500 mcg SQ near injury site
Context: Animal models only
Primary benefit: Theoretical multi-tissue repair (muscle + tendon/ligament)

+ TB-500

Moderate

View TB-500 →

TB-500 (thymosin beta-4 fragment) enhances actin polymerization, cell migration, and angiogenesis—complementary to MGF satellite cell activation. Both upregulated post-injury; combined use presumed additive for muscle regeneration in preclinical models.

MGF: No established dose
TB-500: 2–5 mg SQ weekly
Context: Animal models only
Primary benefit: Satellite cell activation + enhanced migration/angiogenesis