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GHRP-6

Growth hormone axis

Also known as SKF-110679, CIGB-500

A hexapeptide ghrelin receptor agonist. Strongly appetite-stimulating.

Read this first
Two things the vendor literature gets wrong. First, cortisol and prolactin do not only rise 'at high doses', they roughly double at exactly the 1 mcg/kg dose that maximises growth hormone, so the effects cannot be separated by dosing lower. Second, the widely cited '28% increase in food intake in men' comes from a ghrelin study, not a GHRP-6 study.

How it works

Agonist at the ghrelin receptor GHS-R1a on pituitary somatotrophs and on appetite neurons in the arcuate nucleus. It works largely through the body's own GHRH, blocking GHRH cuts the growth hormone response by about 82%, and by opposing somatostatin tone. It also binds CD36, which is the basis of a separate cytoprotective effect unrelated to growth hormone.

SubcutaneousIntravenousIntranasalOral

In the body

Half-life
2.5 hours
Time to peak
18 min
90% gone after
8.3 h
Builds up to
1×
Steady state after about 12.6 h at once, intravenously.
Aug 112:09 PM

Shape of a single dose, modelled as one compartment with first-order absorption. The peak is normalised to 100% because bioavailability and volume of distribution are not published for most of these compounds.

2.5 hours elimination, 7.6 minutes distribution, measured intravenously in nine healthy men. Note this was measured at 100 to 400 mcg/kg, which is 100 to 400 times the dose that saturates growth hormone release, so extrapolating down to a 100 mcg dose is unvalidated. No human subcutaneous pharmacokinetic study exists.

What happens, and when

  1. 0 min, 30 minGrowth hormone pulse peaks 15 to 30 minutes in. Appetite stimulation begins.
  2. 30 min, 2 hPulse largely resolved. Cortisol and prolactin also rise at growth-hormone-saturating doses.
  3. 2 h, 8 hPeptide cleared. Appetite effects can persist several hours in animal studies.

Doses

70 mcg, 100 mcgonce, intravenouslyClinical trial

About 1 mcg/kg intravenously saturates the growth hormone response, peak GH of 68.7 mcg/L against 7.6 at a tenth of the dose.

100 mcg, 300 mcgtwo or three times daily, at least 3 hours apartCommunity practice

The community subcutaneous convention. It is extrapolated from a 1990 intravenous study; no human subcutaneous dose-ranging study has ever been done.

Vial sizes

5 mg

Commonly treated as good for 28 days refrigerated once reconstituted.

Side effects

  • Strong appetite stimulation, the defining feature of this peptide
  • Prolactin and cortisol both roughly double at the dose that maximises growth hormone
  • Increased stage 2 sleep when dosed overnight, along with a nocturnal cortisol rise
  • Water retention, joint and muscle pain, injection site reactions
  • Transient bradycardia at every dose level in 28-day dog toxicology

Cautions

  • Active or suspected malignancy.
  • Cushing's disease or any ACTH-dependent hypercortisolism.
  • Prolactinoma or existing hyperprolactinaemia.
  • Diabetes or impaired glucose tolerance, growth hormone is counter-regulatory.
  • Untreated thyroid dysfunction.

Status

Not approved anywhere. Zero registered trials on ClinicalTrials.gov. A Cuban programme reached phase 3 for acute ischaemic stroke and missed its primary endpoint. Prohibited in sport at all times.

Sources

Reference information for personal record-keeping. Not medical advice, and not a recommendation to use any of these compounds.