GHRP-2

This study was conducted to understand the action of two synthetic GHRPs, GHRP-2 and Hexarelin (HEX), on growth hormone, prolactin, adrenocorticotropic hormone (ACTH), and cortisol concentrations. Two groups of various stages of mature development were evaluated, and both groups experienced a higher GH increase compared to the physiological increase induced by native GHRH. Unfortunately, GHRP-2 may also induce an apparent increase in the levels of ACTH and cortisol.

In one study, two groups were evaluated — one following GHRP-2 exposure and the other with saline — then taken to a buffet meal to measure food intake. The researchers reported that the GHRP-2 models ate an average of 36% more than the saline group, with each model reportedly exhibiting increased food intake when measured against their respective body weight. The energy intake per kilogram of body weight increased up to 136.0±13.0 kJ/kg vs 101.3±10.5 kJ/kg for the placebo group.

Murine models of thermal injury have suggested that GHRP-2 may significantly decrease proinflammatory markers such as IL-6 and E3 ubiquitin ligases (MuRF-1 and MAFbx), which are associated with muscle wasting in critical conditions. The authors also posited that the peptide may directly reduce total muscle protein breakdown in experimental models, suggesting a muscle-sparing action. Case studies have also suggested that the peptide may induce muscle and weight gain.

Studies indicate that GHRP-2 may display antioxidative potential, with researchers noting its possible affinity for CD36, a receptor thought to play a key role in capturing oxidized low-density lipoprotein (OxLDL). This interaction could potentially limit the cellular absorption of OxLDL, which is reputed to contribute to atherogenic processes. In experiments on ApoE(-/-) mouse models, GHRP-2 exposure over 12 weeks seemed to elevate circulating levels of IGF-I between 1.2 to 1.6 times the initial measurements.

A study aimed to explore the potential of GHRP-2 as a diagnostic resource for GH deficiency. The study evaluated research models first tested via insulin tolerance test (ITT). Of these, 77 exhibited normal insulin tolerance and 58 exhibited GH peak levels of less than three. Post overnight fasting, all models were presented GHRP-2. Upon analysis, GH levels peaked after one hour of GHRP-2 in all cases, with results reportedly reproducible upon repetition.

This study was conducted on research models of prolonged hypo-somatotropism, hypogonadism, or hypothyroid complications to evaluate the action of GHRP-2, TRH, and GnRH administered alone and in combination. Over 5 days, groups were presented with placebo, GHRP-2 alone, GHRP-2+TRH, or GHRP-2+TRH+GnRH on varying schedules. Serum samples were collected on the first and last night of the study.