GHRP-2 vs P21 (Cerebrolysin Analog)

Mechanism

GHRP-2 (Growth Hormone Releasing Peptide-2) is a synthetic hexapeptide GHS-R1a agonist that is the most potent of the GHRP family for GH release. It stimulates pituitary GH secretion through the ghrelin receptor while also modulating hypothalamic GHRH and somatostatin pathways. GHRP-2 increases GH, cortisol, prolactin, and ACTH release, but with less appetite stimulation than GHRP-6. It also has demonstrated anxiolytic properties and sleep-promoting effects.

Standard Dosing

Research indicates 100-300 mcg administered 1-3 times daily via subcutaneous injection.

Timing

On empty stomach, bedtime administration preferred. Wait 2+ hours after last meal.

Cycle Duration

8-16 week cycles.

Side Effects

• Water retention
• Moderate hunger increase (less than GHRP-6)
• Cortisol elevation
• Prolactin elevation
• Tingling
• Vivid dreams

Contraindications

• Active cancer
• Cushing's syndrome
• Hyperprolactinemia
• Pregnancy and breastfeeding

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Mechanism

P21 is a tetrapeptide (DGGL — Asp-Gly-Gly-Leu) derived from the most active region of ciliary neurotrophic factor (CNTF, residues 148-151), identified through reverse engineering of Cerebrolysin. An adamantylated glycine enhances BBB permeability and metabolic stability. P21 works through LIF/STAT3 pathway inhibition, BDNF/TrkB/CREB signaling enhancement, and restoration of synaptic proteins (synaptophysin, synapsin I) and glutamate receptors. It promotes neurogenesis and maturation of newborn neurons in the dentate gyrus.

Standard Dosing

Research indicates 750 mcg-1 mg daily via intranasal administration or subcutaneous injection.

Timing

Morning dosing preferred for cognitive effects.

Cycle Duration

4-8 week cycles with 4-week rest periods.

Side Effects

• Mild headache
• Nasal irritation (intranasal)
• Increased appetite (CNTF pathway modulation)
• Vivid dreams

Contraindications

• Pregnancy and breastfeeding
• Active seizure disorders

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