Side-by-side · Research reference

HGH 191AAvsPE 22-28

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-REVIEWED16/47 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

PE 22-28

TREK-1 Antagonist · Pre-Clinical

0.12 nMTREK-1 IC50Djillani 2017

7 AAPeptide lengthDjillani 2017

AnimalEvidence stage

IP · SQ · Once Daily (animal models)Djillani 2017 Pietri 2019

01Mechanism of Action

Parameter

HGH 191AA

PE 22-28

Primary target

Growth hormone receptor (GHR) — JAK2/STAT5 pathway

TREK-1 two-pore-domain potassium channelDjillani 2017 Ma 2020

Pathway

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

TREK-1 channel blockade → Neuronal membrane depolarisation → Enhanced hippocampal excitability → Increased neuroplasticity

Downstream effect

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

Antidepressant-like activity in forced swim test and tail suspension test; reduced A1-like reactive astrocyte activation; neuroprotection via NF-κB pathway modulationDjillani 2017 Cong 2023 Wu 2021

Feedback intact?

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

N/A — direct ion channel blockade; not receptor-mediated endocrine axis

Origin

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

Synthetic truncation of spadin (PE 12-28), itself derived from the sortilin propeptide C-terminus. Residues 22-28: Val-Val-Arg-Gly-Trp-Leu-Arg.Djillani 2017 Mazella 2018

Antibody development

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

Not reported in animal studies

02Dosage Protocols

Parameter

HGH 191AA

PE 22-28

Pediatric GHD

0.024–0.034 mg/kg/day SQ

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

—

Adult GHD

0.004–0.016 mg/kg/day SQ

Start low, titrate based on IGF-1 levels.

—

Turner syndrome

0.045–0.050 mg/kg/day SQ

—

Idiopathic short stature

0.037 mg/kg/day SQ

—

AIDS wasting

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

Short-term indication. Monitor glucose.

—

Frequency

Once daily, typically evening

Evening administration mimics physiological GH pulse.

Once daily

Sustained antidepressant effect over 7+ days.

Evidence basis

FDA-approved / decades of RCT data

Multiple rodent RCTs; behavioral + electrophysiology endpointsDjillani 2017 Qi 2018 Wu 2021

Monitoring

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

—

Duration

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

—

Animal dose (antidepressant)

—

0.3–3 µg/kg IP

Effective in forced swim test, tail suspension test, CUMS models.

Animal dose (neuroprotection)

—

0.03 µg/kg IPPietri 2019

Low-dose TREK-1 activation post-stroke for 7 days, then high-dose blockade.

Onset (animal)

—

Within hours (acute); full effect 4–7 days

Duration (animal)

—

7–28 days testedQi 2018 Pietri 2019

Comparison to fluoxetine

—

PE 22-28 outperforms fluoxetine in CUMS-sensitive rats by day 7

Chronic administration shows superior long-term efficacy.

Human equivalent (extrapolated)

—

Not established — no clinical trials

Allometric scaling from rodent data unavailable.

03Metabolic / Fat Loss Evidence

Parameter

HGH 191AA

PE 22-28

Primary fat target

Visceral and subcutaneous adipose tissue

—

Mechanism

Lipolysis via hormone-sensitive lipase activation, FFA oxidation

—

Effect on lean mass

Significant lean mass increase (protein synthesis, nitrogen retention)

—

Insulin sensitivity

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

—

IGF-1 elevation

Dose-dependent, significant — primary anabolic mediator

—

Glucose metabolism

Hyperglycemia risk, especially high doses (AIDS wasting)

—

Body composition

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

—

Clinical context

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

—

04Side Effects & Safety

Parameter

HGH 191AA

PE 22-28

Injection site reaction

Lipohypertrophy, lipoatrophy, erythema (rotate sites)

—

Fluid retention / Edema

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

—

Glucose intolerance

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

—

Intracranial hypertension

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

—

Slipped capital femoral epiphysis

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

—

Scoliosis progression

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

—

Hypothyroidism

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

—

Cancer risk

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

—

Antibody formation

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

—

Pancreatitis

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

—

Gynecomastia

Adolescent males (physiological during puberty, may be exacerbated)

—

Toxicity (animal)

—

No adverse effects reported at therapeutic doses

Cardiovascular (theoretical)

—

TREK-1 expressed in cardiac tissue; arrhythmia risk unclear

Weight change

—

Not reported in animal studies

Neurological

—

No seizures or behavioral abnormalities noted

Long-term safety

—

Unknown — longest animal study 28 days

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)

PE 22-28

·Human use — no clinical safety data available

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)

PE 22-28

·Cardiac arrhythmia or channelopathy (theoretical TREK-1 cardiac role)

05Administration Protocol

Parameter

HGH 191AA

PE 22-28

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).

Dissolved in sterile saline or vehicle. Intraperitoneal injection, 0.3–3 µg/kg body weight. Once daily administration in rodent behavioral studies.

2. Injection site

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

Shorter peptide length (7 AA) confers improved plasma stability vs 17-AA spadin. Exact storage conditions not detailed in published protocols.Djillani 2017

3. Timing

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

Enhanced CNS bioavailability vs full spadin, likely due to smaller size. Mechanism (passive diffusion vs active transport) not fully characterized.

4. Storage

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

Not established — peptide synthesis methods for research use only. No pharmaceutical-grade formulation available.

5. Needle

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

—

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.

—

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

PE 22-28

— no documented stacks