Side-by-side · Research reference
HGH 191AAvsSermorelin
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
BPhase 3HUMAN-REVIEWED14/43 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
Sermorelin
GHRH 1-29 fragment · Short-acting
SQ · Pre-sleep · 1×/day
01Mechanism of Action
Parameter
HGH 191AA
Sermorelin
Pathway
GHR activation → JAK2/STAT5 → liver IGF-1 synthesis + direct metabolic effects
GHRH-R → Gαs → cAMP → PKA → GH vesicle exocytosisWalker 1994
Downstream effect
Linear growth, lipolysis, protein synthesis, nitrogen retention, carbohydrate metabolism modulation
Pulsatile GH release; subsequent IGF-1 elevationMolteno 2013
Feedback intact?
No — exogenous GH bypasses hypothalamic-pituitary axis, suppresses endogenous pulsatility
Yes — short pulse preserves feedback
Origin
Recombinant DNA technology — 191 AA, identical to pituitary hGH, no methionyl residue
Unmodified active 29-AA fragment of human GHRH (1-44)Walker 1994
Antibody development
Rare — <2% develop binding antibodies, typically non-neutralizing
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02Dosage Protocols
Parameter
HGH 191AA
Sermorelin
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
—
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.
Once daily, pre-sleep
Evidence basis
FDA-approved / decades of RCT data
Phase 3 (Geref pediatric); clinical practiceWalker 1994Molteno 2013
Monitoring
IGF-1, glucose, thyroid function, bone age (children)
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Duration
Years (children until epiphyseal closure); indefinite (adult GHD)
8–12 weeks per cycle
Lower / starter dose
—
100 mcg per dose
Reconstitution
—
Bacteriostatic water
Timing
—
Pre-sleep, fasted preferred
03Metabolic / Fat Loss Evidence
Parameter
HGH 191AA
Sermorelin
Primary fat target
Visceral and subcutaneous adipose tissue
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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
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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)
—
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
Sermorelin
Injection site reaction
Lipohypertrophy, lipoatrophy, erythema (rotate sites)
Mild erythema, transient pain
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).
Contraindicated in active malignancy (GH/IGF-1 axis)
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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Flushing / headache
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Common transient effect
IGF-1 elevation
—
Modest at standard doses
Pregnancy / OB
—
Avoid
Glucose handling
—
Generally neutral
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)
Sermorelin
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
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)
Sermorelin
- ·Untreated diabetes
05Administration Protocol
Parameter
HGH 191AA
Sermorelin
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).
Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL = 250 mcg per 0.1 mL.
2. Injection site
Subcutaneous — rotate sites: abdomen, thigh, buttocks, upper arm. Avoid same site within 1 cm for 2 weeks to prevent lipodystrophy.
SQ — abdomen or thigh. Rotate sites.
3. Timing
Once daily, evening preferred (6–8 PM or pre-sleep). Mimics physiological nocturnal GH secretion. Consistency is critical.
Pre-sleep, fasted.
4. Storage
Unreconstituted: refrigerate 2–8 °C, protect from light. Reconstituted: refrigerate, use within 14–28 days (brand-specific). Do not freeze.
Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.
5. Needle
27–31G, 4–8 mm insulin syringe or pen device. Pinch skin, 45–90° angle depending on subcutaneous thickness.
29–31G, 4–8 mm insulin syringe.
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
ModerateIpamorelin (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
WeakTesamorelin (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
Sermorelin
+ Ipamorelin
StrongSermorelin (GHRH analogue) and ipamorelin (selective GHRP) form the prototypical GHRH+GHRP dual-axis stack at the lowest cost. Both peak within 30 min and produce a sharp physiological GH pulse without cortisol/prolactin elevation.
- Sermorelin
- 200–300 mcg SQ · pre-sleep
- Ipamorelin
- 200–300 mcg SQ · same injection
- Primary benefit
- Pulsatile GH stimulation, recovery, body composition