GHRP-2

What it is

GHRP-2 belongs to the growth hormone releasing peptides, a family of small synthetic peptides developed by the US endocrinologist Cyril Bowers in the 1980s. In 1984 his group described the first of these hexapeptides, which selectively released growth hormone in animals without also raising other pituitary hormones. GHRP-2 is a successor from the same line, also made up of 6 amino acids, partly in the mirror-image D-form, which protects the molecule against breakdown.

The rights went to the Japanese company Kaken, which developed the peptide under the code KP-102. In the US, development as a therapy for growth hormone deficiency was under way and was apparently discontinued. In Japan, by contrast, GHRP-2 was introduced as a diagnostic agent: it is injected once into a vein, and the amount of growth hormone the pituitary gland then releases is measured.

How it works

GHRP-2 mimics ghrelin, the hunger hormone from the stomach. Ghrelin has two major tasks: it triggers growth hormone pulses and signals hunger to the brain. GHRP-2 takes over both via the same receptor, GHSR-1a. Unlike injected growth hormone, the body’s own regulation remains in play: the pituitary gland releases the hormone itself, and feedback via IGF-1 remains active.

The effect is short. In children, the half-life after a single intravenous dose was 0.55 hours, and the growth hormone peak follows within about 60 minutes. Combined with a GHRH signal, the release increases markedly, more so in young adults than in older ones.

GHRP-2 is not entirely selective in this. Besides growth hormone, prolactin, ACTH and the stress hormone cortisol also rise, similar to the related hexarelin. This distinguishes it from the newer ipamorelin, which largely spares these secondary axes.

The test for growth hormone deficiency

The most solid use of GHRP-2 is in diagnostics. In a 2007 validation study, 77 healthy people and 58 patients with confirmed growth hormone deficiency received the peptide intravenously. In the healthy people, growth hormone rose to an average of 84.6 micrograms per liter, in the patients only to 1.36. A cut-off of 15 reliably separated the two groups, the results were highly reproducible, and age and overweight influenced them only slightly.

The test is an alternative to the insulin tolerance test, in which hypoglycemia is induced. It is precisely this strength that makes GHRP-2 valuable as a diagnostic agent: the pituitary gland of a healthy person practically always responds to it.

What users report

In bodybuilding and biohacking circles, GHRP-2 is regarded as a strong, inexpensive growth hormone releaser, often combined with a GHRH analog such as Mod GRF 1-29. A 2026 clinical review that systematically compared forum logs with the study evidence lists mainly increased hunger and, in lab tests, elevated prolactin and cortisol for GHRP-2. For the whole group of these peptides, water retention, joint and muscle complaints and injection-site reactions are added.

These are uncontrolled reports, which we take seriously but do not read as proof of efficacy. The hunger matches the studies exactly. Observations of better sleep or muscle building, on the other hand, have never been tested under controlled conditions.

What the studies show

Tanaka et al. 2014 — the large long-term study

Double-blind, 126 children with growth hormone deficiency, GHRP-2 as a nasal spray at two levels versus placebo, 48 weeks. Height developed the same way in all groups; the change in height standard deviation was 0.07 on placebo and 0.03 and 0.02 on GHRP-2. IGF-1 did not change. The authors conclude that short growth hormone peaks alone are not sufficient.

Bowers et al. 2004 — 30 days of continuous infusion in older people

Healthy older women and men, 17 participants received GHRP-2 continuously under the skin for 30 days, compared with saline. Growth hormone release remained elevated with the pulse pattern preserved, and IGF-1 rose to a stable plateau. Hormone levels were measured, not muscle or function values.

Van den Berghe et al. 2002 — intensive care

Randomized, 33 men with prolonged critical illness, 5 days of placebo, GHRP-2 alone or GHRP-2 combined with other releasing hormones. GHRP-2 alone normalized IGF-1, but only the combinations reduced protein breakdown.

Laferrère et al. 2005 — the hunger finding

Seven lean healthy men, GHRP-2 or saline as an infusion, followed by a free buffet. With GHRP-2 they ate 35.9 percent more, and the composition of the meal remained the same. Growth hormone rose markedly, as expected.

Where the data stop

The decisive step from hormone signal to benefit is not established. In children with growth hormone deficiency, precisely the group for which GHRP-2 was intended as a therapy, IGF-1 rose neither in a small study over 8 months nor in the double-blind study over 48 weeks, and growth did not improve. An IGF-1 rise was seen only under continuous infusion in older people and in the critically ill, that is, under conditions that have little to do with the usual occasional injection.

There is not a single study on muscle building, fat loss, sleep or recovery in healthy adults. A 2026 review places GHRP-2 in the second of four evidence levels: clinical diagnostics and small human studies on hormone levels and appetite, no long-term safety data.

Status, approval and legal

GHRP-2 is not approved as a medicine in Germany and the EU and is sold as a research peptide on the gray market. In Japan it is established as a diagnostic agent for the growth hormone test. Since September 29, 2023, the US Food and Drug Administration (FDA) has listed GHRP-2 for injection and as a nasal spray in Category 2 of its interim policy for outsourcing facilities (503B outsourcing facilities), that is, among the substances that may present significant safety risks and should not be used in compounding. In sport it is prohibited at all times, listed by name on the 2026 WADA list under S2.2.4 and in the annex of the German Anti-Doping Act, and it is detectable in urine together with its metabolite. We do not give dosage information for non-approved substances.

Safety

In the short term, GHRP-2 was well tolerated in the studies; in a pediatric study over 8 months no side effects occurred, and under 30 days of continuous infusion the safety labs remained normal. Typical effects are increased hunger and a rise in prolactin and cortisol, which can be confusing in lab results. The FDA is aware of reports of increased insulin requirements, infections, pancreatitis and deaths in critically ill study participants, without a causal relationship having been established. Because the growth axis is a growth signal, the peptide is considered problematic in cancer, but a clinical cancer signal has not been established. Long-term data, data on pregnancy and interactions are missing, and the content of gray-market products is unverified.

Sources

• Tanaka et al., Clinical Pediatric Endocrinology 2014
• Bowers et al., Journal of Clinical Endocrinology and Metabolism 2004
• Van den Berghe et al., Clinical Endocrinology 2002
• Laferrère et al., Journal of Clinical Endocrinology and Metabolism 2005
• Chihara et al., European Journal of Endocrinology 2007
• Arvat et al., Peptides 1997
• Mericq et al., Journal of Clinical Endocrinology and Metabolism 1998
• Pihoker et al., Journal of Clinical Endocrinology and Metabolism 1998
• Dominikowski et al., Frontiers in Endocrinology 2026
• FDA, bulk drug substances that may present significant safety risks, as of April 22, 2026