GHRP-2

Ghrelin, a gut hormone, acts on the growth hormone secretagogue receptor (GHS-R) and has two well-described effects: it releases growth hormone and it stimulates appetite². GHRP-2 is a synthetic agonist of that receptor. According to the Japanese package insert, it binds GHS receptors and promotes pituitary growth hormone release mainly through an action on the hypothalamus; in animal studies, removing the pituitary or damaging hypothalamic areas weakened the effect⁶. After an intravenous injection, blood growth hormone peaks within about an hour, which is why a low peak can flag deficiency¹. It leaves the blood quickly and appears to be eliminated mainly through bile rather than urine⁶.

Most human data are diagnostic. In a Japanese study of 77 healthy people and 58 adults with severe growth hormone deficiency confirmed by insulin tolerance testing, an intravenous GHRP-2 test gave far lower growth hormone peaks in patients than in healthy volunteers, with good reproducibility, supporting a diagnostic cut-off¹.

In 7 lean, healthy men, a subcutaneous GHRP-2 infusion lasting several hours raised growth hormone and increased food intake at a buffet meal by about 36 percent compared with saline². Repeated use was explored only in small studies in the 1990s and early 2000s: six children with growth hormone deficiency given injections for eight months had more night-time growth hormone release and faster growth, without a rise in IGF-1³, and in 14 adults with prolonged critical illness, a five-day infusion of GHRP-2 combined with TRH, compared with placebo, brought IGF-1 toward normal and lowered a marker of protein breakdown⁴. ClinicalTrials.gov lists no studies using it as the study drug. Its potential misuse by athletes led to urine detection methods for doping control⁵.

GHRP-2 is approved in Japan, as the prescription injectable GHRP Kaken 100 (pralmorelin hydrochloride), only for diagnosing growth hormone deficiency⁶. It is not FDA-approved, and we found no approval for it as a treatment.

The Japanese package insert lists a feeling of warmth as the most common reaction (16 percent), with others including sweating, thirst, hunger, drowsiness, dizziness, nausea or stomach discomfort, flushing, headache, low blood pressure and minor blood-count shifts. It is contraindicated in pregnancy. With related drugs, pituitary apoplexy (sudden bleeding or tissue death in a pituitary tumor) has been reported in people with pituitary adenomas⁶. Repeated use has been studied only in small groups, too few to describe rare or long-term effects³.

1. Chihara et al., Eur J Endocrinol 2007PubMed
2. Laferrère et al., J Clin Endocrinol Metab 2005PubMed
3. Mericq et al., J Clin Endocrinol Metab 1998PubMed
4. Van den Berghe et al., J Clin Endocrinol Metab 1999PubMed
5. Okano et al., Rapid Commun Mass Spectrom 2010PubMed
6. PMDA package insert: GHRP Kaken 100 (Japan)pmda.go.jp