Side-by-side · Research reference
SermorelinvsThymosin α-1
Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.
APhase 3Reviewed14/43 cited
BPhase 3Reviewed8/39 cited
Sermorelin
GHRH 1-29 fragment · Short-acting
SQ · Pre-sleep · 1×/day
Thymosin α-1
Immune modulator · Approved (some countries)
SQ · 2× weekly · 6+ months for chronic indications
01Mechanism of Action
Parameter
Sermorelin
Thymosin α-1
Primary target
Pituitary GHRH receptorWalker 1994
Toll-like receptor 9 (TLR9) + T-cell maturation pathwayCamerini 2001
Pathway
GHRH-R → Gαs → cAMP → PKA → GH vesicle exocytosisWalker 1994
TLR9 activation → ↑ IFN-α + IL-2 + IFN-γ → enhanced T-cell function + dendritic cell maturationIyer 2007
Downstream effect
Pulsatile GH release; subsequent IGF-1 elevationMolteno 2013
Restored T-cell function, improved viral clearance, anti-tumour adjuvant effectsIyer 2007
Feedback intact?
Yes — short pulse preserves feedback
—
Origin
Unmodified active 29-AA fragment of human GHRH (1-44)Walker 1994
Synthetic 28-AA peptide identical to natural Tα-1 isolated from thymus extractCamerini 2001
Antibody development
—
—
02Dosage Protocols
Parameter
Sermorelin
Thymosin α-1
Frequency
Once daily, pre-sleep
2× weekly (Mon/Thu typical)
Lower / starter dose
100 mcg per dose
0.8 mg per injection
Evidence basis
Phase 3 (Geref pediatric); clinical practiceWalker 1994Molteno 2013
Phase 3 + approved (35+ countries as Zadaxin)Iyer 2007
Duration
8–12 weeks per cycle
6–12 months for chronic indications
Reconstitution
Bacteriostatic water
Sterile water for injection per vial label
Timing
Pre-sleep, fasted preferred
No specific time
Half-life
~12 min (plasma)Molteno 2013
Shorter than tesamorelin (~26 min) — simpler GHRH analogue.
~2 hours plasma; tissue effect days
04Side Effects & Safety
Parameter
Sermorelin
Thymosin α-1
Injection site reaction
Mild erythema, transient pain
Erythema, mild discomfort
Flushing / headache
Common transient effect
—
IGF-1 elevation
Modest at standard doses
—
Cancer risk
Contraindicated in active malignancy (GH/IGF-1 axis)
No signal — used as adjuvant in oncology
Pregnancy / OB
Avoid
Avoid
Glucose handling
Generally neutral
—
GI symptoms
—
Rare nausea
Fatigue
—
Common during initial weeks
Fever / flu-like
—
Mild interferon-like response possible
Autoimmune
—
Theoretical risk; caution in active autoimmune disease
Absolute Contraindications
Sermorelin
- ·Active malignancy
- ·Pregnancy / breastfeeding
- ·Disrupted hypothalamic-pituitary axis
Thymosin α-1
- ·Pregnancy / breastfeeding
- ·Hypersensitivity to peptide
- ·Concurrent immunosuppressant therapy (transplant patients)
Relative Contraindications
Sermorelin
- ·Untreated diabetes
Thymosin α-1
- ·Active autoimmune disease
- ·Severe immunocompromised state without supervision
05Administration Protocol
Parameter
Sermorelin
Thymosin α-1
1. Reconstitution
Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL = 250 mcg per 0.1 mL.
Add 1 mL sterile water per 1.6 mg vial → 1.6 mg/mL.
2. Injection site
SQ — abdomen or thigh. Rotate sites.
SQ — abdomen, thigh, or upper arm. Rotate sites.
3. Timing
Pre-sleep, fasted.
2× weekly, e.g. Monday + Thursday.
4. Storage
Lyophilised: room temp, light-protected. Reconstituted: refrigerate ≤30 days.
Lyophilised: refrigerate. Reconstituted: refrigerate, use within 24 h.
5. Needle
29–31G, 4–8 mm insulin syringe.
27–31G, 4–8 mm insulin syringe.
06Stack Synergy
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
Thymosin α-1
— no documented stacks