Head to head

GHRP-2 vs MK-677

GH secretagogue

Side-by-side on appetite control, dosing, kinetics and evidence — with an honest verdict at the end.

Verdict

Route decides this one, not potency

On overlap and evidence these are close enough that the data cannot pick a winner. What it can tell you is that GHRP-2 means a needle and a reconstitution step and MK-677 does not. For most people that, plus whether they will actually keep to once daily dosing, is what really decides it.

What you are actually choosing between

Both are classed here as growth hormone secretagogues, so this is a within-class choice: the mechanism is broadly shared and what separates them is kinetics, route, and how much has actually been tested.

The overlap is appetite control, recovery and sleep, and muscle growth. On this site's goal weighting — an editorial priority score, not a measure of effect size — GHRP-2 rates 3/5 for appetite control and MK-677 rates 5/5.

The evidence

GHRP-2 sits one step firmer: approval from a regulator somewhere, though not a current FDA or EMA label — registered in Japan as pralmorelin for a single-dose diagnostic test, not chronic use. MK-677 has controlled human trials behind it, without an approval — never approved, and trials flagged higher fasting glucose. One tier is a real difference but not a decisive one; it should not on its own settle the choice.

How they differ in practice

GHRP-2 is a subcutaneous injection and an intramuscular injection; MK-677 is taken by mouth. That is the difference most people actually feel: GHRP-2 means reconstituting a vial and injecting; MK-677 does not require either. If needles are the deciding factor, this line settles it before any of the rest matters.

The kinetics are roughly 24× apart — 24 h for MK-677 against 1 h for GHRP-2 — and yet both are dosed once daily. That schedule is convention rather than clearance, which is worth knowing before you assume the two behave the same way between doses.

Committed time differs: GHRP-2 runs 12 weeks, MK-677 runs 16 weeks.

Source notes

What the evidence actually says

Verbatim, so you can check the verdict above against what it was built from.

GHRP-2

Synthetic hexapeptide ghrelin receptor (GHS-R1a) agonist. Unusually for this corner of the market it has real human data: it has been studied as a growth hormone secretagogue in published dose-response work, and the same molecule is registered in Japan as pralmorelin for use as a single-dose diagnostic test of growth hormone deficiency. That diagnostic use is a one-off intravenous challenge, not a chronic subcutaneous protocol, so the human evidence supports the fact that it releases growth hormone rather than the community habit of dosing it daily for months. It is not approved for physique or anti-ageing use anywhere. It is less selective than ipamorelin: expect measurable prolactin and cortisol elevation, which is the usual reason people switch away from it. The 100-300 mcg per dose range, often split into two or three doses a day, comes from practice rather than from a label.

MK-677 (Ibutamoren)

Orally active, long-acting ghrelin receptor (GHS-R1a) agonist that raises GH and IGF-1 for around 24 hours per dose. It has been through multiple human trials, including a two-year study in older adults, but was never approved for any indication and trials also flagged increased fasting glucose and reduced insulin sensitivity. It is a non-peptide small molecule, so it is taken by mouth rather than injected.

Side by side

The numbers

GHRP-2 compared with MK-677
Attribute	GHRP-2	MK-677
Class	GH secretagogue	GH secretagogue
Routes	Subcutaneous, Intramuscular	Oral
Dose range	100 mcg–300 mcg (typical 200 mcg)	10 mg–25 mg (typical 15 mg)
Frequency	Once daily	Once daily
Half-life	1 h	24 h
Cycle length	12 weeks	16 weeks
Experience	Intermediate	Intermediate
Evidence	Approved elsewhere	Controlled human trials
Contraindications	Pregnant / nursing Active malignancy Under 18	Pregnant / nursing Active malignancy Under 18
Side effects	Raises prolactin and cortisol more than ipamorelin does — this is its main practical drawback, and it scales with dose, so pushing past roughly 300 mcg per injection buys little extra growth hormone while making the hormonal spillover worse Hunger spike within about half an hour of dosing, which works against a cut Water retention, morning puffiness, and numb or tingling hands Head rush, flushing or brief light-headedness just after injection Blunted response over months of uninterrupted daily use, so it is usually cycled Injection site redness or itching	Pronounced increase in appetite, often within the first few days Water retention, puffiness in the face and ankles, and rapid scale weight gain Raised fasting blood glucose and reduced insulin sensitivity — a real concern for anyone prediabetic or diabetic, and worth monitoring with bloodwork on longer runs Lethargy or grogginess the morning after a pre-bed dose Numbness or tingling in the hands, sometimes carpal-tunnel-like Vivid dreams and deeper but occasionally disrupted sleep Mild joint aches at higher doses

Turn a typical dose into a mark on the syringe: GHRP-2

Goals

Where they overlap, and where they do not

Goal	GHRP-2	MK-677
appetite control	GHRP-2: 3/5	MK-677: 5/5
recovery and sleep	GHRP-2: 3/5	MK-677: 5/5
muscle growth	GHRP-2: 3/5	MK-677: 4/5
injury repair	GHRP-2: 2/5	MK-677: 2/5
longevity	GHRP-2: 1/5	MK-677: 2/5
fat lossone only	GHRP-2: 2/5	MK-677: —
skin and hairone only	GHRP-2: —	MK-677: 2/5

They overlap on 5 goals and diverge on 2. Weights are this site’s editorial priority score out of 5 — how central a goal is to why people use a compound. They are not effect sizes and two 5s do not mean two equal results.

Go deeper

MonographGHRP-2Mechanism, protocol, storage, sources.MonographMK-677 (Ibutamoren)Mechanism, protocol, storage, sources.ToolReconstitution calculatorTurn either dose above into a mark on the syringe.

Other comparisons with these two

Educational information only, not medical advice. Talk to a licensed clinician before starting, changing, or stopping anything.