Side-by-side · Research reference

SermorelinvsThymalin

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

APhase 3Reviewed14/43 cited

BHuman-MechanisticDraft12/40 cited

Sermorelin

GHRH 1-29 fragment · Short-acting

100–500 mcgPer doseMolteno 2013

Phase 3Evidence levelWalker 1994 Molteno 2013

~12 minHalf-lifeMolteno 2013

SQ · Pre-sleep · 1×/day

Thymalin

Immune restorer · Russian peptide bioregulator

5–10 mgPer cycle doseKhavinson 2002

HumanMechanisticKhavinson 2002

HoursHalf-life (est)

IM · Daily for 5–10 days · 1-2×/year

01Mechanism of Action

Parameter

Sermorelin

Thymalin

Primary target

Pituitary GHRH receptorWalker 1994

T-cell precursors + thymus-axis maturation pathwayKhavinson 2002

Pathway

GHRH-R → Gαs → cAMP → PKA → GH vesicle exocytosisWalker 1994

Modulation of T-cell differentiation + thymic hormone restoration in age-involuted thymusKhavinson 2002

Downstream effect

Pulsatile GH release; subsequent IGF-1 elevationMolteno 2013

Restored T-cell populations, improved immune surveillance, reduced infection rates in elderlyKhavinson 2002

Feedback intact?

Yes — short pulse preserves feedback

—

Origin

Unmodified active 29-AA fragment of human GHRH (1-44)Walker 1994

Polypeptide fraction isolated from calf thymus extractKhavinson 2002

Antibody development

—

02Dosage Protocols

Parameter

Sermorelin

Thymalin

Standard dose

100–500 mcg per injectionMolteno 2013

5–10 mg / day IM × 5–10 daysKhavinson 2002

Frequency

Once daily, pre-sleep

Once daily during cycle

Lower / starter dose

100 mcg per dose

2.5 mg / day

Evidence basis

Phase 3 (Geref pediatric); clinical practiceWalker 1994 Molteno 2013

Russian clinical + in vitroKhavinson 2002

Duration

8–12 weeks per cycle

5–10 day cycles, 1–2× per year

Reconstitution

Bacteriostatic water

Saline or bacteriostatic water

Timing

Pre-sleep, fasted preferred

Morning preferred

Half-life

~12 min (plasma)Molteno 2013

Shorter than tesamorelin (~26 min) — simpler GHRH analogue.

Hours (estimated)

04Side Effects & Safety

Parameter

Sermorelin

Thymalin

Injection site reaction

Mild erythema, transient pain

Mild erythema at IM site

Flushing / headache

Common transient effect

—

IGF-1 elevation

Modest at standard doses

—

Cancer risk

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

—

Pregnancy / OB

Avoid

Glucose handling

Generally neutral

—

Allergic reaction

—

Rare hypersensitivity to bovine-derived polypeptide

Autoimmune flare

—

Theoretical risk in active autoimmune disease

Long-term safety

—

Limited Western data

Absolute Contraindications

Sermorelin

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

Thymalin

·Pregnancy / breastfeeding
·Bovine protein hypersensitivity

Relative Contraindications

Sermorelin

·Untreated diabetes

Thymalin

·Active autoimmune disease
·Concurrent immunosuppressant therapy

05Administration Protocol

Parameter

Sermorelin

Thymalin

1. Reconstitution

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

Add 1–2 mL saline or bacteriostatic water per 10 mg vial.

2. Injection site

SQ — abdomen or thigh. Rotate sites.

Intramuscular — deltoid or gluteal. Rotate sites.

3. Timing

Pre-sleep, fasted.

Morning preferred during cycle.

4. Storage

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

Lyophilised: refrigerate, light-protected. Reconstituted: use immediately.

5. Needle

29–31G, 4–8 mm insulin syringe.

23–25G, 25–38 mm IM needle.

06Stack Synergy

Sermorelin

+ Ipamorelin

Strong

View Ipamorelin →

Sermorelin (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

Raun 1998 Walker 1994

Thymalin

+ Thymosin α-1

Moderate

View Thymosin α-1 →

Thymalin is a polypeptide complex; Thymosin α-1 is a single purified peptide. Both target the thymus-axis but at different levels — Thymalin restores broad thymic signaling; Tα-1 provides a specific molecular activator. Anecdotally combined for elderly immune support.

Thymalin: 5–10 mg IM · daily × 7 days
Thymosin α-1: 1.6 mg SQ · 2× weekly during the cycle
Primary benefit: Broad thymic restoration + targeted immune activation

Khavinson 2002 Camerini 2001