Side-by-side · Research reference

GHRP-6vsRetatrutide

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

APhase 1Reviewed10/36 cited

BPhase 2Reviewed10/41 cited

GHRP-6

Hexapeptide GHRP · Strong appetite stimulant

100–200 mcgPer doseBowers 1990

Phase 1Evidence levelBowers 1990

~15 minHalf-lifeMalagón 1999

SQ · Multiple sites · 1–3×/day

Retatrutide

Triple-receptor agonist · Phase 3

1–12 mgWeekly doseJastreboff 2023

24.2%Body-weight ↓Jastreboff 2023

~6 daysHalf-life (est)

SQ · Abdomen · Once weekly

01Mechanism of Action

Parameter

GHRP-6

Retatrutide

Primary target

Ghrelin receptor (GHS-R1a)Bowers 1990

GLP-1R + GIPR + Glucagon receptor (triple agonism)Jastreboff 2023

Pathway

GHS-R1a → Gαq → Ca²⁺ → GH release; central appetite driveBowers 2002

Triple-receptor activation → ↑insulin (GLP-1+GIP), ↓gastric emptying, ↑lipid handling, ↑energy expenditure (glucagon component)Jastreboff 2023

Downstream effect

GH pulse + strong appetite stimulation; modest IGF-1 elevationBowers 2002

Maximal weight loss across class. Glucagon component drives lipolysis and energy expenditure beyond GLP-1+GIP aloneJastreboff 2023

Feedback intact?

—

Origin

Synthetic hexapeptide; first-generation GHRP from Bowers groupBowers 1990

Synthetic peptide engineered for balanced affinity at three incretin / glucagon receptorsJastreboff 2023

Antibody development

—

02Dosage Protocols

Parameter

GHRP-6

Retatrutide

Standard dose

100–200 mcg per injectionBowers 1990

12 mg / week (max efficacy)Jastreboff 2023

Phase 2 trial dose. Phase 3 dosing TBD.

Frequency

1–3× per day

Once weekly

Lower / starter dose

50 mcg per dose

—

Evidence basis

Phase 1 + clinical practiceBowers 1990

Phase 2 trial; Phase 3 ongoingJastreboff 2023

Duration

8–12 weeks on / 4 off

Indefinite for chronic indication (presumed)

Reconstitution

Bacteriostatic water

Investigational; not commercially available

Timing

Pre-meal preferred for appetite support

Any time of day

Half-life

~15 minMalagón 1999

~6 days (estimated from class)

Titration schedule

—

2 mg → 4 mg → 8 mg → 12 mg over 16 weeks

04Side Effects & Safety

Parameter

GHRP-6

Retatrutide

Hunger

Pronounced — defining feature vs ipamorelin

—

Cortisol elevation

Mild

—

Prolactin elevation

Mild

—

Injection site reaction

Mild

—

Cancer risk

Contraindicated in active malignancy

—

Pregnancy / OB

Avoid

Avoid (insufficient data)

GI symptoms

—

Nausea, vomiting, diarrhea (very common, dose-dependent)Jastreboff 2023

Heart rate

—

↑ resting HR (3–7 bpm at 12 mg)Jastreboff 2023

Glucose handling

—

Glycemic improvement; rare hyperglycemia from glucagon component

Pancreatitis risk

—

Class warning

Thyroid C-cell tumours

—

Class warning (presumed)

Absolute Contraindications

GHRP-6

·Active malignancy
·Pregnancy / breastfeeding

Retatrutide

·MTC personal or family history (presumed class effect)
·Pregnancy / breastfeeding

Relative Contraindications

GHRP-6

·Severe insulin resistance (appetite-driven caloric load)

Retatrutide

·Severe gastroparesis
·History of pancreatitis
·Severe cardiovascular disease (HR signal)

05Administration Protocol

Parameter

GHRP-6

Retatrutide

1. Reconstitution

Add 2 mL bacteriostatic water to 5 mg vial → 2.5 mg/mL.

Investigational peptide. Research vials reconstituted with bacteriostatic water per label.

2. Injection site

SQ — abdomen. Rotate sites.

SQ — abdomen, thigh, or upper arm. Rotate weekly.

3. Timing

Pre-meal for appetite support; pre-sleep for GH alignment.

Once weekly, same day.

4. Storage

Lyophilised: room temp. Reconstituted: refrigerate ≤30 days.

Refrigerate 2–8 °C. Light-protected.

5. Needle

29–31G, 4–8 mm insulin syringe.

27–31G, 4–8 mm insulin syringe.