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The peptide literature, summarized and graded.

Every paper distilled to a plain-language summary with an honest evidence grade — from strong human trials to animal-only signals. 2 papers indexed and counting.

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Filtered by #GHRP-2 · clear

Animal only

Diurnal and Daily Variations in Growth Hormone and Growth Hormone Stimulation Test in Male Cynomolgus Monkeys.

This study characterized growth hormone (GH) secretion patterns and responsiveness to exogenous GH-releasing hormone (GHRH) in adult male cynomolgus monkeys, with the goal of evaluating their suitability as a model for pituitary toxicity research. Two groups of ten animals were used to assess diurnal and day-to-day GH variation via serial serum sampling, while a separate four-animal-per-group crossover examined GH responses to intravenous pralmorelin hydrochloride (a GHRH analog) versus saline. GH was measured by ELISA. The study found a diurnal pattern resembling that of humans, with GH rising in the late morning, dipping around midday, and peaking at night. Considerable inter- and intra-individual daily variation was also observed over five consecutive days. In the stimulation test, GHRH-treated animals showed significantly higher GH concentrations at 0.5 and 1 hour post-administration compared to controls. The authors conclude that cynomolgus monkeys share key GH secretion characteristics with humans and may serve as a relevant non-clinical model. Limitations include small sample sizes, male-only subjects, and the non-human primate setting, meaning direct translation to human physiology or clinical applications requires caution.

#GHRP-2

In vivo (Athens, Greece) · Jan 2026DOI ↗

Animal only

Pharmacokinetic evaluation of ipamorelin and other peptidyl growth hormone secretagogues with emphasis on nasal absorption.

This study compared the pharmacokinetics of five peptidyl growth hormone secretagogues — ipamorelin (NNC 26-0161), NNC 26-0194, NNC 26-0235, GHRP-2, and GHRP-6 — in male rats using multiple routes of administration, with a particular focus on nasal delivery. Following intravenous bolus injection, all peptides showed biexponential plasma concentration decline. Ipamorelin stood out with a systemic plasma clearance approximately five times lower than GHRP-6. Excretion routes differed: ipamorelin was primarily cleared via urine, while GHRP-6 and the two NNC peptides were predominantly excreted in bile. Metabolic stability was moderate for ipamorelin and the NNC peptides, with 60–80% of administered doses recoverable as intact peptide from bile and urine combined. Intranasal bioavailability of ipamorelin was estimated at approximately 20%, while NNC 26-0235, NNC 26-0194, and GHRP-2 achieved approximately 50% nasal bioavailability. The authors concluded that nasal delivery appears to be a promising route for this peptide class. Key limitations include exclusive use of animal subjects (male rats), meaning findings may not directly translate to humans, and the study did not assess pharmacodynamic or safety endpoints.

#ipamorelin #GHRP-2 #GHRP-6

Xenobiotica; the fate of foreign compounds in biological systems · Nov 1998DOI ↗