Ipamorelin, a new growth-hormone-releasing peptide, induces longitudinal bone growth in rats.

<-it was new in 1999 when this study was published.

“Ipamorelin is a potent synthetic pentapeptide which has distinct and specific growth hormone (GH)-releasing properties. With the objective of investigating the effects on longitudinal bone growth rate (LGR), body weight (BW), and GH release, ipamorelin in different doses (0, 18, 90 and 450 microg/day) was injected s.c. three times daily for 15 days to adult female rats. After intravital tetracycline labelling on days 0, 6, and 13, LGR was determined by measuring the distance between the respective fluorescent bands in the proximal tibia metaphysis. Ipamorelin dose-dependently increased LGR from 42 microm/day in the vehicle group to 44, 50, and 52 microm/day in the treatment groups{So there was no cap at the dosage so far but there was a point of dimishing returns}. There was also a pronounced and dose-dependent effect on BW gain. The treatment did not affect total IGF-I levels, IGFBPs, or serum markers of bone formation and resorption. The number of tartrate-resistant acid phosphatase-positive multinuclear cells in the metaphysis of the tibia did not change significantly with treatment. The responsiveness of the pituitary to a provocative i.v. dose of ipamorelin or GHRH showed that the plasma GH response was marginally reduced after ipamorelin, but unchanged after GHRH{So there is a negative feedback mechanism in response to ipamorelin}. The pituitary GH content was unchanged by ipamorelin treatment.”

4-month old Sprague-Dawley rats were used.  Unlike with longitudinal bone growth there were no diminishing returns with body weight gain.

This study doesn’t quite give enough evidence to be confident in Ipamorelin’s height increasing abilities such as growth plate images for example but it’s definitely worth investigating.