Side-by-side · Research reference

HexarelinvsHGH 191AA

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

APhase 1HUMAN-REVIEWED19/45 cited

BFDA-ApprovedHUMAN-REVIEWED0/75 cited

Hexarelin

Hexapeptide GHRP · Cardio-tropic

100–200 mcgPer doseSmith 1996

Phase 1Evidence levelGhigo 1997

~70 minHalf-lifeSemenistaya 2010

SQ · Multiple sites · 1–3×/day

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

01Mechanism of Action

Parameter

Hexarelin

HGH 191AA

Primary target

Ghrelin receptor (GHS-R1a) + cardiac CD36Smith 1996 Ghigo 1997

Growth hormone receptor (GHR) — JAK2/STAT5 pathway

Pathway

GHS-R1a → Gαq → Ca²⁺ → GH release. CD36 engagement → direct cardio-tropic actionGhigo 1997

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

Downstream effect

Strong GH pulse + IGF-1 elevation; cardio-protective effects in animal MI modelsGhigo 1997

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

Feedback intact?

Yes initially; tachyphylaxis with chronic useGhigo 1997

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

Origin

Synthetic hexapeptide His-D-2-Methyl-Trp-Ala-Trp-D-Phe-Lys-NH₂Smith 1996

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

Antibody development

—

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

02Dosage Protocols

Parameter

Hexarelin

HGH 191AA

Standard dose

100–200 mcg per injectionSmith 1996

—

Frequency

1–2× per day max (tachyphylaxis with chronic 3× daily)

Once daily, typically evening

Evening administration mimics physiological GH pulse.

Lower / starter dose

50 mcg per dose

—

Evidence basis

Phase 1 / Phase 2 trialsSmith 1996 Ghigo 1997

FDA-approved / decades of RCT data

Duration

4–8 weeks on / 4–8 weeks off (tachyphylaxis mitigation)

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

Reconstitution

Bacteriostatic water

—

Timing

Pre-sleep + fasted preferred

—

Half-life

~70 minSemenistaya 2010

—

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.

Monitoring

—

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

03Metabolic / Fat Loss Evidence

Parameter

Hexarelin

HGH 191AA

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

Hexarelin

HGH 191AA

Cortisol elevation

Modest at high dosesGhigo 1997

—

Prolactin elevation

Modest at high dosesGhigo 1997

—

Hunger

Strong appetite increase via ghrelin agonism

—

Tachyphylaxis

Receptor desensitisation with chronic dosingGhigo 1997

—

Cardiac effects

Direct cardio-tropic; potential benefit in MI but unstudied in humansGhigo 1997

—

IGF-1 elevation

Strong; monitor with chronic high-dose use

—

Cancer risk

Contraindicated in active malignancy (GH/IGF-1 axis)

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

Pregnancy / OB

Avoid

—

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)

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)

Absolute Contraindications

Hexarelin

·Active malignancy
·Pregnancy / breastfeeding
·Disrupted hypothalamic-pituitary axis

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)

Relative Contraindications

Hexarelin

·Untreated diabetes
·Severe hyperprolactinemia

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)

05Administration Protocol

Parameter

Hexarelin

HGH 191AA

1. Reconstitution

Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL = 250 mcg per 0.1 mL.

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).

2. Injection site

SQ — abdomen or thigh. Rotate sites.

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

3. Timing

Pre-sleep + fasted preferred. Cycle on/off to avoid tachyphylaxis.

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

4. Storage

Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.

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

5. Needle

29–31G, 4–8 mm insulin syringe.

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

Hexarelin

+ CJC-1295 (no DAC)

Strong

View CJC-1295 (no DAC) →

Hexarelin (GHRP) + CJC-1295-no-DAC (GHRH analogue) is the higher-amplitude variant of the standard GHRH+GHRP stack. Hexarelin produces a stronger pulse than ipamorelin but with cortisol + prolactin signal — choose this stack for maximum GH amplitude when side-effect tolerance is acceptable. Cycle aggressively.

Hexarelin: 100 mcg SQ · pre-sleep
CJC-1295 (no DAC): 100 mcg SQ · same injection
Primary benefit: Maximum GH pulse amplitude (with side-effect signal)

Smith 1996 Teichman 2006

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