GHRP-2 / GHRP-6 / Hexarelin

What are GHRP-2, GHRP-6 and hexarelin?

Growth hormone-releasing peptides (GHRP) are short synthetic peptides that stimulate growth hormone release from the pituitary. A six-amino-acid peptide that was one of the first of this family (His-DTrp-Ala-Trp-DPhe-Lys-NH2, the sequence known as GHRP-6) strongly released growth hormone in 18 healthy men in a study published in 1990. The authors proposed that the peptide acts through a pathway independent of GHRH (growth hormone-releasing hormone) and reflects a physiological system not yet identified. ^[1]

That system was later identified as the ghrelin system. Ghrelin is a hormone produced in the stomach that stimulates both growth hormone release and appetite; GHRP-2 is a synthetic agonist of the receptor to which this hormone binds (the growth hormone secretagogue receptor). ^[2] GHRP-2 and hexarelin are described as non-natural synthetic derivatives (super-analogs) of GHRP-6 with potent growth hormone-releasing activity. ^[3] Hexarelin also appears on the WADA list under the name examorelin; the international name of GHRP-2 is pralmorelin. ^[12]

Other substances also stimulate the same receptor: ipamorelin is covered in the Ipamorelin guide, and ibutamoren, an orally taken non-peptide ghrelin mimetic, in the MK-677 (Ibutamoren) guide. What the “research peptide” label means is covered in a separate guide: What does research peptide mean?

What effects of these peptides have been measured in humans?

Most of the human data come from studies in healthy volunteers in the 1990s that measured hormone levels for several hours after a single dose. Participant numbers range from 6 to 18.

Growth hormone release

That these peptides briefly raise growth hormone was seen consistently in many small studies. When GHRP-6 was given together with GHRH, the response was larger than the sum of the separate effects of the two substances; the authors interpreted this as a sign that the two act through different pathways. ^[1] With hexarelin, the response in repeated intravenous tests was of similar size. ^[4]

These findings are laboratory values. A growth hormone level rising for a few hours does not mean a measured benefit for muscle mass, fat percentage, recovery or aging. A 2026 narrative review also writes that human evidence for an effect of hexarelin on body composition is limited, that expectations in this area are largely inferred from GH and IGF-1 increases, and that they do not rest on controlled studies designed for these outcomes. ^[10]

Prolactin, ACTH and cortisol

GHRPs do not stimulate only growth hormone. In the 1997 comparative study, GHRP-2 and hexarelin raised prolactin, ACTH and cortisol to a similar degree; the authors concluded that these peptides are “not completely selective.” Their strength in stimulating ACTH and cortisol is similar to that of CRH, which is used in the stimulation test of the stress hormone axis; the prolactin stimulation was lower than with TRH. ^[3] In the 1990 study with GHRP-6, prolactin and cortisol rose about 2-fold only at the highest dose. ^[1]

The mode of administration can change the result. In a one-day study in six young men given hexarelin subcutaneously two or three times a day, 24-hour GH secretion rose; no change was seen in prolactin, ACTH, cortisol or IGF-1 levels. In the same people, hexarelin given intravenously at the end of the day raised all four hormones; earlier administrations reduced the GH response and abolished the ACTH and cortisol response. ^[5] The FDA also lists a possible effect on cortisol among the safety concerns for GHRP-6. ^[11]

GHRP-2 and appetite

The two basic effects of ghrelin are stimulating growth hormone release and appetite. In the 2005 study, 7 healthy, lean men received a subcutaneous GHRP-2 or saline infusion for 270 minutes, followed by an all-you-can-eat meal. During GHRP-2, participants ate a mean of 35.9% more, and every participant’s intake rose; the macronutrient distribution of the food eaten did not change. ^[2] This study measures a single meal; the effect on weight or body fat with repeated use was not measured. A 2026 review describes consistent appetite increase as one of the characteristic effects of GHRP-6 as well, and reports that appetite increase and mild weight gain were noted in long-term oral use of GHRP-2 in children with growth hormone deficiency. ^[10]

What happens with long-term use?

Long-term human data exist almost only for hexarelin. In the study in which adults received hexarelin subcutaneously twice a day for 16 weeks, the GH response to the hexarelin test (area under the curve) was 19.1 µg/L·hour at baseline, fell to 12.3 at week 4 and 10.5 at week 16, and returned to 19.4 four weeks after treatment was stopped. Serum IGF-1 and IGFBP-3 did not change significantly. Total body fat, lean body mass and bone mineral density were also no different from baseline at week 16. The authors concluded that repeated use partly and reversibly blunts the GH response and that the biological effect of this regimen on the GH–IGF-1 axis appears “minimal.” ^[6] The abstract of the study does not state the number of participants or a placebo group.

The 2026 review writes that direct human evidence on the effect of GHRP-6 on body composition is limited and that there is no controlled efficacy study; that therapeutic use of GHRP-2 other than for diagnosis has remained limited and is not supported by broad regulatory approval. ^[10]

Hexarelin and the heart

Hexarelin has also been studied for its claimed ability to affect heart muscle independently of growth hormone. In a 2002 study, 13 patients with severe left heart failure (8 dilated, 5 ischemic cardiomyopathy) received a single intravenous dose of hexarelin. In the patients in the ischemic group, left ventricular ejection fraction rose from 22.6% at baseline to a peak of 26.2%; it did not change significantly in the dilated group. Other hemodynamic measurements did not change. ^[7] The study had no placebo group, the comparison was made with previously studied healthy and GH-deficient groups, and only the immediate effect of a single dose was measured. These data do not show a treatment benefit in heart disease; the effect and safety of repeated use in heart patients were not examined in this study.

Is there a licensed use?

The only known licensed use in this family is the diagnostic use of GHRP-2. The KEGG drug database classifies pralmorelin hydrochloride as a diagnostic agent with a product registration in Japan, used in endocrine function tests. ^[9] In the validation study in Japan, a single intravenous dose of GHRP-2 was given to 77 healthy people and 58 patients with severe GH deficiency identified by an insulin tolerance test. Peak GH averaged 1.36 µg/L in patients and 84.6 µg/L in the healthy group; a cutoff of 15 µg/L corresponded to the diagnostic value of 3 µg/L in the insulin tolerance test. ^[8] This use is a one-time hormone test in a hospital; it is not treatment or regular use.

No licensed use has been defined for GHRP-6 and hexarelin. According to the 2026 review, human data on GHRP-6 are limited to phase 1 and small mechanistic studies and there is no controlled efficacy study; hexarelin has remained limited to phase 1 and phase 2 studies in growth hormone deficiency in children and in adult endocrine patients, and there is no body composition study. ^[10]

What are the risks?

There are no long-term safety data. What is known comes from small short-term studies and regulatory assessments.

• Blood sugar: The FDA lists blood sugar elevation due to reduced insulin sensitivity among the safety concerns for GHRP-6. For GHRP-2, with the note that causality was not established, it mentions reports of increased insulin requirement to maintain blood sugar, and of death, infection and pancreatitis in severely ill study participants. ^[11]
• Hormone balance: Increases in prolactin, ACTH and cortisol are known unwanted effects of these peptides. ^[3] A review lists, among the side effects reported in people using such peptides on their own, elevated prolactin and cortisol, appetite changes, blood sugar disturbance, fluid retention, muscle and joint pain and injection site reactions. ^[10]
• Appetite: GHRP-2 markedly increased food intake in a single infusion. ^[2]
• Product quality and immune response: According to the FDA, GHRP-2 and GHRP-6 may carry a risk of immune response through some routes of administration because of aggregation and peptide-related impurities; the presence of a non-natural amino acid in GHRP-2 makes product characterization difficult. ^[11] The same review stresses that the content and dose of products in the unsupervised supply chain are uncertain. ^[10]

The effect of hexarelin on the heart was studied in heart patients only with a single dose; the safety of repeated use in these patients was not studied. ^[7] Side effects reported for peptide use in general are collected in a separate guide: Peptide side effects

FDA, WADA and Türkiye: what is the legal status?

United States (FDA)

The FDA evaluates substances nominated for use as bulk ingredients in compounded drugs prepared by pharmacies and places those that may present significant safety risks in “category 2.” GHRP-2 (for injection and intranasal use) and GHRP-6 have been in the 503B category 2 table, which applies to outsourcing facilities, since September 29, 2023. Hexarelin does not appear on this page. ^[11] This list is not a drug approval; it concerns the use of the substances in compounded manufacturing.

Sport (WADA)

In WADA’s list effective January 1, 2026, under S2.2.4 “growth hormone-releasing factors,” among the examples of “GH-releasing peptides,” alexamorelin, examorelin (hexarelin), GHRP-1, GHRP-2 (pralmorelin), GHRP-3, GHRP-4, GHRP-5 and GHRP-6 are named. Substances in section S2 are prohibited at all times, in and out of competition. ^[12]

Türkiye

TİTCK (Turkish Medicines and Medical Devices Agency) lists no product containing GHRP-2 (pralmorelin), GHRP-6 or hexarelin in its Licensed Human Medicinal Products List dated October 16, 2026. ^[13] Article 19 of Law No. 1262 on Pharmaceutical and Medicinal Preparations (İspençiyari ve Tıbbi Müstahzarlar Kanunu) punishes with imprisonment from one to five years those who manufacture unlicensed preparations and those who knowingly sell, offer for sale or have others sell preparations manufactured in this way. The same article provides the same penalty for those who sell, market or advertise a product that is not a preparation with the claim that it diagnoses or treats diseases; importing preparations made abroad without a license for commercial purposes counts as smuggling. ^[14]

The general legal framework of peptides in Türkiye and the national anti-doping organization are covered in a separate guide: Are peptides legal?

Evidence table: claim, population and limits

Limits of this guide

This page summarizes the published human data on GHRP-2, GHRP-6 and hexarelin and the decisions of official bodies. It gives no dose, cycle, preparation, administration technique or product sourcing information; the administrations in the studies are only the description of that study. Suspected growth hormone deficiency or excess is a medical condition that needs to be evaluated with hormone tests and requires assessment by an endocrinology specialist.