GHRP-2 and GHRP-6 study findings

What did the GHRP-6 studies in people measure?

The only GHRP-6 study in people found for this page is a 1992 paper. It measured growth hormone release in five healthy men, and in nine short children whose growth hormone was low to different degrees. GHRP-6 was given by mouth, and also into a vein for comparison. In the men, growth hormone rose well above its starting level and fell back within about three hours. In four of the nine children, the response matched the men. In the other five, it was low or could not be detected. The paper reports hormone levels only. It does not show any effect on body composition or appetite.

The 1992 team wanted to know whether a peptide taken by mouth could release growth hormone at all. By their sums, GHRP-6 by mouth had about 0.3% of the activity of the form given into a vein. How the peptides work covers the half-life and distribution-volume figures from the same paper.

The group was small: five men and nine children, as the abstract on PubMed describes. Read the paper as a measurement of one hormone response in a few people. That is the most the study can show.

What is pralmorelin (GHRP-2) approved for in Japan?

In Japan, pralmorelin hydrochloride is approved as a diagnostic for growth hormone secretion failure. Its approval number is 21600AMZ00573000, and sales started in February 2005. A diagnostic is a test, not a treatment. The drug is given to see how strongly the pituitary gland responds. For severe deficiency, the label sets a cut-off at a growth hormone peak of 15 ng/mL, or 9 ng/mL when measured against a recombinant (lab-made) reference standard. A nanogram (ng) is a billionth of a gram, so ng/mL means nanograms in each millilitre. The label says that other findings and the lab method also matter.

A 2004 drug profile explains the idea behind the test. In healthy people, the peptide raises growth hormone strongly: in men and women, in people with and without obesity, and across age groups. In people with growth hormone deficiency, the rise is much smaller. The authors used a ROC (receiver-operating characteristic) analysis, a standard way to pick the best cut-off between two groups. It put the line between deficiency and healthy controls at a growth hormone peak of 15.0 micrograms per litre. That profile was written before the Japanese launch.

The label reports two Japanese trials. The first tested 89 healthy people, including children who were short but healthy (normal short stature). Their peak growth hormone ranged from 15.88 to 345.06 ng/mL, with an average of 84.60. The response was somewhat lower in people aged 40 and over, and in women after menopause. It did not differ by sex or by degree of obesity. The second tested 60 patients already diagnosed with severe deficiency. Their peak ranged from 0.05 or below to 14.79 ng/mL, with an average of 1.37.

What did the anti-doping urine study measure?

Semenistaya and colleagues studied five growth hormone-releasing peptides, with one volunteer for each. Each volunteer received a peptide through the nose, and the team checked what showed up in the urine. GHRP-2 and two of its breakdown products, GHRP-2 free acid and GHRP-2 (1-3) free acid, were found for up to 47 hours. GHRP-6 mostly left the body unchanged. It was found at 23 hours, and its breakdown products were found for 12 hours. The study was written to give sport labs a test method. It was not a trial of effects. With one person per peptide, it cannot show how people differ.

The authors say detection time depends on each person's metabolism, the form of the product and the route. So read the figures as examples from one volunteer each, not as fixed numbers. Do peptides show up on drug tests explains how testing labs use this kind of method paper.

Evidence limits

What has research not shown about GHRP-2 and GHRP-6?

A rise in a hormone is a biomarker: a lab number that stands in for something else. It is not an outcome. Knowing that growth hormone goes up does not tell you whether muscle, fat, sleep or recovery change, and these papers did not measure those things. The same caution applies to forum posts and seller pages. They are personal stories, not controlled studies.

Some regulators have gone further than the research. The FDA puts GHRP-6, and GHRP-2 for two named routes, in a category of bulk substances that raise significant safety risks (FDA 503B list, updated 21 March 2025). The side-effects page sets that out next to the label's own warnings.