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GHRP-6

GHRP-6 (growth hormone-releasing peptide-6; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) is a synthetic hexapeptide growth hormone secretagogue that binds the ghrelin/GHS-R1a receptor and triggers a burst of growth hormone (GH) release through a combined hypothalamic and pituitary mechanism. It is an unapproved research chemical with no approved human therapeutic indication and no long-term human safety data; product sold to consumers is not pharmaceutical-grade and purity/sterility cannot be assumed. The single most important danger is that GHRP-6 is not selective for GH: human studies consistently show it also drives release of ACTH, cortisol, and prolactin, so users are self-administering an agent that perturbs the entire stress and reproductive hormone axis, not just GH. Because it is a potent ghrelin-receptor agonist it also causes marked appetite stimulation. Additional concerns are shared with any intervention that chronically raises GH/IGF-1: impaired glucose tolerance/insulin resistance, fluid retention (edema, carpal-tunnel-type symptoms, joint pain), and a theoretical mitogenic risk that contraindicates it in anyone with cancer. Human evidence is limited to small, mostly single-dose pharmacodynamic studies; there are no trials establishing safety or benefit for the muscle-building, anti-aging, or recovery purposes for which it is used. This monograph leads with risk and defers all endocrine management to a physician.

Clinical readoutPeptide · gh-secretagogue
Hepatic strainLow
CardiovascularModerate
HPTA suppressionNone
Half-life
38 min
Route
Studied in humans by in…
Evidence
D
Active
GH response is rapid an…
38 min1.3 h1.9 h2.5 h3.1 h
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ Short; the circulating peptide is cleared within roughly 15-60 minutes. Well-characterized human PK parameters are not established in the peer-reviewed literature.
Pharmacology

Mechanism of action

GHRP-6 is a synthetic peptide agonist of the growth hormone secretagogue receptor (GHS-R1a), the same receptor bound by endogenous ghrelin. It releases GH through a dual, complementary action: at the hypothalamus (its predominant site of action, shown by the near-complete loss of GHRP-6-induced GH release in patients with hypothalamo-pituitary disconnection) and directly at pituitary somatotrophs. Intracellularly it acts independently of cAMP, instead stimulating phosphatidylinositol (PI) turnover, protein kinase C, and mobilization of intracellular calcium. It synergizes strongly with GHRH and blunts somatostatin tone. GHS-R activation is not confined to the GH axis: GHRP-6 also stimulates the hypothalamic-pituitary-adrenal axis (raising ACTH and cortisol), raises prolactin, stimulates arginine vasopressin release (preclinically), and drives appetite/food intake via central ghrelin-receptor pathways.
Kinetics

Pharmacokinetics

Half-life

Short; the circulating peptide is cleared within roughly 15-60 minutes. Well-characterized human PK parameters are not established in the peer-reviewed literature.

Active duration

GH response is rapid and transient after IV/SC dosing: GH rises within ~15 minutes, peaks around 15-30 minutes, and returns toward baseline by ~120 minutes. Tachyphylaxis (desensitization) of the GH response occurs with repeated/continuous dosing.

Route

Studied in humans by intravenous, subcutaneous, and intranasal routes; oral absorption is poor and largely ineffective for GH/ACTH release (an enteric oral dose failed to raise GH/ACTH/cortisol, whereas intranasal dosing was active). Route and dose strongly determine the endocrine response.

Metabolism & clearance

As a small peptide it is degraded by plasma and tissue peptidases (proteolysis) with fragment clearance via the kidney. Not a substrate for hepatic CYP metabolism. PK note is for washout/monitoring context only, not for evading testing.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Acute pulsatile increase in serum growth hormone (dose-related), documented in healthy adults and children after IV, SC, intranasal, and (weakly) oral dosing
  • Downstream rise in IGF-1 with repeated dosing (inferred from the GH secretagogue class; chronic oral secretagogue MK-0677 raised IGF-1 by ~84% in an RCT)
  • Marked appetite stimulation / increased food intake via ghrelin-receptor agonism (robust preclinical evidence; expected pharmacologic effect in humans)
  • Concurrent, non-selective stimulation of ACTH and cortisol (HPA axis activation) - an unwanted effect, not a benefit
  • Concurrent elevation of prolactin
  • Alteration of sleep architecture (increased stage 2 non-REM sleep after GHRP-6; the related secretagogue hexarelin reduced slow-wave/deep sleep)
  • No established, human-trial-proven effect on muscle mass, fat loss, injury recovery, or anti-aging endpoints
Safety

Adverse effects by system

Cardiovascular

No direct human cardiovascular outcome data for GHRP-6. Concerns are extrapolated: sustained GH/IGF-1 elevation is associated with fluid retention, edema, and (in chronic GH excess such as acromegaly) cardiac hypertrophy; the MK-0677 secretagogue trial excluded patients with uncontrolled hypertension and congestive heart failure. Ghrelin-receptor agonists show preclinical cardiac effects, but no controlled human safety signal is established. Treat cardiovascular risk as unknown but plausibly adverse with chronic use.

Hepatic

No evidence of direct hepatotoxicity; GHRP-6 is an injectable peptide and is not 17-alpha-alkylated. No human liver-injury data specific to GHRP-6. Indirect hepatic/metabolic effects could occur via GH/IGF-1-mediated insulin resistance, but this is not directly documented for GHRP-6.

Endocrine / HPTA

The defining endocrine liability: GHRP-6 is non-selective and reproducibly raises ACTH, cortisol, and prolactin in human studies in addition to GH. It also stimulates GH-axis feedback and, preclinically, vasopressin. It does not act as a classic gonadal-axis suppressant the way anabolic androgens do, but elevated prolactin and disturbed HPA signaling can secondarily disrupt libido, mood, and gonadal function. Repeated dosing causes GH-response desensitization.

Reproductive

No human fertility or pregnancy safety data. Prolactin elevation can impair reproductive/sexual function. Contraindicated in pregnancy and breastfeeding due to absence of safety data and mitogenic/hormonal activity.

Neuropsychiatric

No dedicated human psychiatric safety studies. HPA-axis activation (raised cortisol) and disrupted sleep architecture are physiologically capable of affecting mood, anxiety, and sleep quality; hexarelin (a close analog) reduced deep slow-wave sleep. Neuropsychiatric effects are plausible but not well characterized.

Renal

No specific human renal toxicity data. Fluid retention/sodium retention associated with GH elevation can affect volume status; peptide fragments are renally cleared. Overall renal risk unquantified.

Hematologic

No known specific hematologic toxicity and no adequate human hematologic data for GHRP-6.

Dermatologic

No specific dermatologic adverse-effect data for GHRP-6. Injection-site reactions are a general risk of any injectable; sterility of non-pharmaceutical product cannot be assumed.

Recovery

HPTA suppression & recovery

Suppression: GHRP-6 is not a classic hypothalamic-pituitary-gonadal (HPTA) suppressant like anabolic-androgenic steroids; there is no evidence it directly shuts down endogenous testosterone production. Its dominant endocrine disturbance is off-target activation of the HPA axis (cortisol/ACTH) and elevation of prolactin, which can secondarily affect gonadal/sexual function.

Because GHRP-6 does not cause androgen-type gonadal suppression, SERM-based 'post-cycle' recovery protocols are neither validated nor indicated for it, and no dual-SERM approach should ever be used. Any perceived hormonal disturbance (e.g., elevated prolactin, altered cortisol, low libido, menstrual changes) must be evaluated with bloodwork and managed by a qualified endocrinologist rather than self-treated. Conservative default: stop the compound and seek clinical evaluation if hormonal symptoms arise.

Bloodwork & vitals

Monitoring

Recommended labs & checks
IGF-1Fasting glucoseHbA1cFasting insulin (insulin sensitivity)ProlactinMorning cortisol and ACTHThyroid panel (TSH, free T4)Lipid panelComplete blood countComprehensive metabolic panel (electrolytes, renal, hepatic)

Cadence: Baseline before any use and periodic re-check (e.g., approximately every 3 months) under the supervision of a physician/endocrinologist; sooner if symptoms develop. This is a clinician-directed monitoring framework, not an endorsement of use.

Warning signs — seek care
  • New or worsening hyperglycemia symptoms (excessive thirst, frequent urination, blurred vision)
  • Numbness/tingling or wrist pain (carpal-tunnel-type symptoms from fluid retention)
  • Peripheral edema or rapid weight gain from fluid
  • Joint pain or swelling
  • Persistent headache or visual field changes
  • Breast discharge (galactorrhea), gynecomastia, or loss of libido (prolactin elevation)
  • Mood disturbance, anxiety, or disrupted sleep
  • Signs of injection-site infection (redness, swelling, fever)
Do not use if

Contraindications

  • Active or prior malignancy, or high cancer risk (GH/IGF-1 elevation is mitogenic; theoretical tumor-promotion concern)
  • Diabetes mellitus or impaired glucose tolerance (secretagogues worsen insulin sensitivity; MK-0677 trial excluded diabetics)
  • Pregnancy and breastfeeding (no safety data; hormonal activity)
  • Pituitary tumor, acromegaly, or other GH-excess state
  • Prolactinoma or pre-existing hyperprolactinemia
  • Active proliferative diabetic retinopathy
  • Uncontrolled hypertension or congestive heart failure (per related secretagogue trial exclusions)
  • Any acute critical illness (GH secretagogues alter stress-axis hormones)
  • Use of non-sterile, non-pharmaceutical-grade material (infection/contaminant risk)
Combinations

Interaction profile

  • MajorWith insulin: Metabolic / glucose
  • ModerateWith another GH secretagogue: Metabolic / glucose
  • ModerateWith growth hormone: Metabolic / glucose
  • ModerateWith IGF-1: Metabolic / glucose
  • ModerateWith a GLP-1 / incretin agonist: Metabolic / glucose
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • This is an unapproved research chemical with no long-term human safety data; the safest course is not to use it. If someone is using it, they should do so only with physician oversight and baseline plus periodic bloodwork.
  • Understand it is not GH-selective: it predictably raises cortisol and prolactin, so it can worsen stress-hormone load, mood, and sleep quality, not just raise GH.
  • Screen out and avoid entirely if you have any history of cancer, diabetes/prediabetes, pituitary disease, uncontrolled hypertension, heart failure, or are pregnant/breastfeeding.
  • Monitor glucose and HbA1c - GH/IGF-1 elevation can impair insulin sensitivity; stop and see a clinician if fasting glucose or HbA1c rise.
  • Stop use and seek medical care for: carpal-tunnel-type numbness/tingling, significant edema or rapid fluid weight gain, joint pain, persistent headache or vision changes, breast discharge, or signs of injection-site infection.
  • Never combine with other hormonal agents in an attempt to amplify effects; do not use SERMs or any 'post-cycle' protocol for this compound - they are not indicated and dual-SERM regimens must never be used.
  • Any hormonal abnormality found on labs (prolactin, cortisol, thyroid, glucose) should be managed by a qualified endocrinologist, not self-treated.
  • Do not use to maximize GH output or as part of a mass/leanness optimization plan; there is no human evidence of benefit for those goals and the risks are real and under-characterized.
Evidence

Citations (16)

Every clinical claim above is tied to a primary source. Overall evidence grade D — this compound lacks adequate human data; claims rest on preclinical or mechanistic evidence.

  1. 01

    GHRP-6 is a synthetic hexapeptide GH secretagogue that releases GH via a dual, complementary hypothalamic and pituitary mechanism.

    ReviewGrowth hormone-releasing peptide (GHRP).PMID 9893708 ↗

  2. 02

    GHRP-6's main GH-releasing action is exerted at the hypothalamic level and it synergizes with GHRH (GHRP-6-induced GH release was nearly abolished in patients with hypothalamo-pituitary disconnection).

    CohortPMID 7883854 ↗

  3. 03

    GHRP-6 stimulates GH via a cAMP-independent pathway involving phosphatidylinositol turnover, protein kinase C, and calcium in human pituitary somatotroph cells.

    PreclinicalPMID 7772238 ↗

  4. 04

    Functional GH secretagogue (ghrelin) receptors mediating GHRP-6 action are expressed in human pituitary tissue; in human fetal pituitary cells GHRP-6 released GH.

    PreclinicalHuman fetal pituitary expresses functional growth hormone-releasing peptide receptors.PMID 9435437 ↗

  5. 05

    In healthy men, repeated IV GHRP-6 (4 x 50 microg) increased not only GH but also ACTH and cortisol and increased stage 2 sleep, demonstrating non-selective HPA-axis activation.

    RCTGrowth hormone-releasing peptide-6 stimulates sleep, growth hormone, ACTH and cortisol release in normal man.PMID 7617137 ↗

  6. 06

    GHRP-6 endocrine effects are route- and dose-dependent; enteric oral dosing did not raise GH/ACTH/cortisol whereas intranasal dosing raised GH, indicating poor oral efficacy.

    RCTPMID 10336729 ↗

  7. 07

    Oral GHRP-6 (300 microg/kg) released GH in children with short stature, comparable to GHRH.

    CohortGrowth hormone-releasing effect of oral growth hormone-releasing peptide 6 (GHRP-6) administration in children with short stature.PMID 7581965 ↗

  8. 08

    The GH response to GHRP-6 (1 microg/kg IV) is blunted in states of glucocorticoid excess / Cushing's syndrome.

    RCTDifferent effects of GHRP-6 and GH-releasing hormone on GH release in endogenous and exogenous hypercortisolism.PMID 9274702 ↗

  9. 09

    GH secretagogues of the GHRP-6 family (hexarelin, GHRP-2) reproducibly raise prolactin, ACTH, and cortisol in healthy humans, confirming lack of GH selectivity.

    RCTPMID 10195374 ↗

  10. 10

    Hexarelin, a close GHRP-6 analog, elevated prolactin, cortisol and ACTH in healthy volunteers via a non-opioid mechanism.

    RCTThe effect of an opiate antagonist on the hormonal changes induced by hexarelin.PMID 7586608 ↗

  11. 11

    Hexarelin (GHS analog) decreased slow-wave (deep) sleep while stimulating GH, ACTH, cortisol and prolactin during sleep in healthy volunteers.

    RCTHexarelin decreases slow-wave sleep and stimulates the secretion of GH, ACTH, cortisol and prolactin during sleep in healthy volunteers.PMID 15177700 ↗

  12. 12

    GH secretagogues including GHRP-6 stimulate the HPA axis and prolactin and stimulate vasopressin release (preclinical hypothalamic model).

    PreclinicalPMID 10444309 ↗

  13. 13

    GHRP-6 and related ghrelin-receptor agonists stimulate appetite/food intake and activate feeding-related brain regions.

    PreclinicalPMID 21843570 ↗

  14. 14

    Ghrelin's orexigenic action is mediated by the GHS receptor (blocked by the GHRP-6 antagonist [D-Lys3]GHRP-6), supporting GHRP-6's appetite-stimulating pharmacology.

    PreclinicalPMID 24211488 ↗

  15. 15

    Chronic oral GH secretagogue therapy (MK-0677) raised IGF-1 by ~84% in an RCT; diabetics and those with uncontrolled hypertension/CHF were excluded and glucose/insulin were monitored, reflecting class metabolic and cardiovascular caution.

    RCTPMID 15066065 ↗

  16. 16

    GH secretagogues raise IGF-1, show tachyphylaxis of the GH response, and their GH-releasing effect varies with age; endocrine (PRL/ACTH/cortisol) activity is a recognized feature of the class.

    ReviewPMID 9667794 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice