Side-by-side · Research reference

HGH 191AAvsIGF-1 LR3

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-REVIEWED10/58 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

IGF-1 LR3

IGF-1 Analogue · Research

3–10×Potency vs IGF-I

Low IGFBPBinding affinity

ResearchStatus

Research only · SQ typical in animal models

01Mechanism of Action

Parameter

HGH 191AA

IGF-1 LR3

Primary target

Growth hormone receptor (GHR) — JAK2/STAT5 pathway

IGF-1 receptor (IGF-1R)McTavish 2009

Pathway

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

IGF-1R → IRS-1 → PI3K/Akt → Cell proliferation, protein synthesis, anti-apoptosisMuhlbradt 2009

Downstream effect

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

Enhanced cell proliferation, muscle anabolism, inhibition of apoptosis, increased telomerase activity

Feedback intact?

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

No — exogenous IGF analogue bypasses GH-mediated regulation

Origin

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

Synthetic 83-AA analogue: 13-AA N-terminal extension + Arg substitution at position 3

Antibody development

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

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02Dosage Protocols

Parameter

HGH 191AA

IGF-1 LR3

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 / 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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Research dose (animal models)

—

Variable by protocol and species

In vivo murine atherosclerosis studies used sustained delivery.

In vitro typical concentration

—

10–1000 ng/mLThomas 2007

Dose-dependent effects on follicle growth and estradiol production.

Half-maximal stimulation

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0.6 nM LR3 vs 1.5 nM native IGF-1Price 2004

2.5-fold greater potency in lung fibroblast proliferation.

Human use

—

Not FDA-approved; no published human trials

03Metabolic / Fat Loss Evidence

Parameter

HGH 191AA

IGF-1 LR3

Primary fat target

Visceral and subcutaneous adipose tissue

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Mechanism

Lipolysis via hormone-sensitive lipase activation, FFA oxidation

IGF-1R activation → lipolytic signaling; secondary to anabolic effects

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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Direct lipolytic evidence

—

Minimal — primarily anabolic/anti-apoptotic in literature

Atherosclerotic plaque effects

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Reduced stenosis and core size in ApoE-KO micevon 2011

Plaque stabilization via vSMC phenotype modulation, not direct fat loss.

Human data

—

None published

04Side Effects & Safety

Parameter

HGH 191AA

IGF-1 LR3

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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Hypoglycemia risk

—

Theoretical — IGF-1 analogues can lower blood glucose

Excessive cell proliferation

—

Mitogenic signaling; theoretical tumor promotion risk

Telomerase activation

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2–10-fold increase in prostate cancer cells (PC-3, DU-145, LAPC-4)Wetterau 2003

Critically involved in cancer cell immortalization.

Oocyte degeneration

—

Increased oocyte degeneration at high doses (≥1000 ng/mL) in bovine folliclesThomas 2007

Unregulated anabolism

—

Bypasses physiological GH/IGF-1 feedback; no pulsatility control

Unknown human safety profile

—

No published human trials; safety data absent

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)

IGF-1 LR3

·Active malignancy or history of cancer
·Not approved for human use

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)

IGF-1 LR3

·Diabetes or glucose intolerance
·Family history of cancer

05Administration Protocol

Parameter

HGH 191AA

IGF-1 LR3

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).

IGF-1 LR3 is not FDA-approved for human use. All administration data derives from animal or in vitro studies.

2. Injection site

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

Subcutaneous or intraperitoneal injection in animal models. In vitro: added directly to culture medium at concentrations of 10–1000 ng/mL.Thomas 2007

3. Timing

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

Lyophilised powder reconstituted in sterile water or buffered saline per manufacturer protocol. Store at 2–8 °C after reconstitution.

4. Storage

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

Enhanced stability vs native IGF-1 due to reduced IGFBP binding; exact half-life in vivo not fully characterized in humans.

5. Needle

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

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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

IGF-1 LR3

+ GHRP-6

Multi-pathway

View GHRP-6 →

GHRP-6 stimulates endogenous GH release, which drives hepatic IGF-1 synthesis. IGF-1 LR3 provides exogenous, IGFBP-resistant IGF signaling. Combining upstream GH stimulation with downstream IGF receptor activation creates a dual-pathway anabolic effect. However, this bypasses natural feedback and carries compounded mitogenic risk.

GHRP-6: 100–200 mcg SQ · 2–3× daily
IGF-1 LR3: Research doses variable · post-workout typical in animal models
Note: Research context only — no human protocols exist
Primary benefit: Theoretical maximal anabolic signaling (GH + IGF axes)

+ Ipamorelin

Multi-pathway

View Ipamorelin →

Ipamorelin (selective GHRP) stimulates pulsatile GH release without cortisol/prolactin elevation. IGF-1 LR3 directly activates IGF-1R independent of GH. This stack targets both upstream (GH secretion) and downstream (IGF receptor) nodes but eliminates physiological feedback, raising safety concerns around unchecked proliferation.

Ipamorelin: 200–300 mcg SQ · evening
IGF-1 LR3: Research doses only · timing variable
Caution: No human data; animal/in vitro only
Primary benefit: Dual-axis anabolic signaling (theoretical)