Hexarelin, a synthetic GH-releasing peptide, is a powerful stimulus of GH secretion in pubertal children and in adults but not in prepubertal children and in elderly subjects.
Bellone. J J; Bartolotta. E E; Sgattoni. C C; Aimaretti. G G; Arvat. E E; Bellone. S S; Deghenghi. R R; Ghigo. E E
Key Findings
- In pubertal children and young adults, a single IV dose of hexarelin (2 µg/kg) caused a large increase in GH levels, comparable to the classic GH‑releasing test (arginine + GHRH).
- Pre‑pubertal children showed a weaker GH response to hexarelin, not significantly different from GHRH alone.
- Elderly subjects had a modest GH rise with hexarelin, but it was still lower than the response to arginine + GHRH.
Practical Outcomes
- For biohackers interested in GH elevation, hexarelin could be an effective IV option for younger adults, but its benefit drops sharply with age. The need for intravenous administration and the lack of oral formulations limit everyday use. Older individuals should not expect a strong GH boost from hexarelin alone.
Summary
Hexarelin is a synthetic peptide that can trigger a strong release of growth hormone (GH) when given by IV injection, especially in teenagers and young adults. It works less well in kids before puberty and in older adults, where the GH boost is modest.
Abstract
GH-releasing peptides (GHRPs) and their non-peptidly mimetics are synthetic molecules which possess marked, dose-related and reproducible GH-releasing effect even after oral administration. Their potent stimulatory effect on GH secretion suggested that GHRP could be useful as provocative test on the diagnosis of GH deficiency. We compared the GH response to the maximal effective dose of Hexarelin (2 micrograms/kg i.v.), an hexapeptide belonging to GHRP family, with that of GHRH (1 microgram/kg i.v.) alone and combined with arginine (ARG, 0.5 g/kg i.v.), which likely acts via inhibition of hypothalamic somatostatin release. We studied 6 prepubertal (4 boys and 2 girls, age 2.6-12.2 yr) and 6 pubertal children with normal short stature (3 boys and 3 girls, age 10.3-14.4 yr) as well as 12 normal young adults (6 males and 6 females, age 22-30 yr) and 12 normal elderly subjects (6 males and 6 females, age 53-79 yr). In prepubertal children, the GH response to HEX (19.0 +/- 4.6 micrograms/l; 611.5 +/- 121.4 micrograms/l/h) was lower than that to GHRH (27.4 +/- 12.7 micrograms/l; 1209.0 +/- 590.9 micrograms/l/h) but this difference did not attain statistical significance. Both these responses were, in turn, lower (p < 0.05) than that to ARG + GHRH (57.9 +/- 15.1 micrograms/l; 2483.6 +/- 696.6 micrograms/l/h). In pubertal children, the GH response to HEX (67.6 +/- 12.7 micrograms/l; 2755.3 +/- 547.3 micrograms/l/h) was higher than that to ARG + GHRH (49.1 +/- 8.9 micrograms/l; 2554.1 +/- 356.6 micrograms/l/h) but this difference did not attain statistical significance; both these responses were, in turn, clearly higher (p < 0.05) than that to GHRH alone (23.1 +/- 7.9 micrograms/l; 1004.8 +/- 214.3 micrograms/l/h). In young adults, the GH response to HEX 60.9 +/- 8.0 micrograms/l; 2401.0 +/- 376.2 micrograms/l/h) was similar to that to ARG + GHRH (68.9 +/- 11.7 micrograms/l; 3035.7 +/- 466.6 micrograms/l/h) and both were clearly higher (p < 0.001) than that to GHRH alone (21.6 +/- 3.6 micrograms/l; 790.0 +/- 137.0 micrograms/l/h). In elderly subjects, the GH response to HEX (22.4 +/- 4.9; 855.0 +/- 199.0 micrograms/l/h) was higher (p < 0.01) than that to GHRH (3.6 +/- 0.8 micrograms/l; 151.8 +/- 24.6 micrograms/l/h) but lower (p < 0.05) than that to ARG + GHRH (48.1 +/- 4.6 micrograms/l; 1758.2 +/- 149.1 micrograms/l/h). In conclusion, GHRPs are a powerful stimulus of GH secretion in pubertal children and young adults only. On the other hand, the age-related variations in the GH response to GHRPs probably limit their reliability for the evaluation of GH releasable pool in prepubertal children and elderly subjects.
Study Information
pubmed
1998
10.1007/bf03347334