Ghrelin mimetics

Pradhan G, Samson SL, Sun Y. Ghrelin: much more than a hunger hormone. Curr Opin Clin Nutr Metab Care. 2013 Nov;16(6):619-24.
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"Introduction - Ghrelin is a 28-aa Ser3 acylated peptide, and its functionally relevant endogenous receptor is growth hormone secretagogue receptor (GHS-R). Ghrelin is a key regulator of nutrient sensing, meal initiation, and appetite. Apart from its orexigenic effect, research in the last decade has shown that ghrelin has regulatory roles in in many organs and systems. Ghrelin signaling has increasingly been recognized as a key regulator of obesity, insulin resistance and diabetes; intriguingly, many of these regulatory functions appear to be independent of ghrelin's effect on food intake. This current review is focused on the most recent findings of ghrelin in glucose homeostasis, energy-homeostasis, heart disease, muscular atrophy, bone metabolism, and cancer development/progression."

Lange T, Thomas A, Görgens C, Bidlingmaier M, Schilbach K, Fichant E, Delahaut P, Thevis M.  Comprehensive insights into the formation of metabolites of the ghrelin mimetics capromorelin, macimorelin
and tabimorelin as potential markers for doping con Biomed Chromatogr. 2021 Jan 17:e5075. doi: 10.1002/bmc.5075. Epub ahead of print. PMID: 33458843.
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Abstract
Analytical methods to determine the potential misuse of the ghrelin mimetics capromorelin (CP-424,391), macimorelin (macrilen, EP-01572) and tabimorelin (NN703) in sports were developed. Therefore, different extraction strategies, i.e. solid-phase extraction, protein precipitation, as well as a "dilute-and-inject" approach, from urine and EDTA-plasma were assessed and comprehensive in vitro/in vivo experiments were conducted, enabling the identification of reliable target analytes by means of high resolution mass spectrometry. The drugs' biotransformation led to the preliminary identification of 51 metabolites of capromorelin, 12 metabolites of macimorelin and 13 metabolites of tabimorelin. Seven major metabolites detected in rat urine samples collected post-administration of 0.5-1.0 mg of a single oral dose underwent in-depth characterization, facilitating their implementation into future confirmatory test methods. In particular, two macimorelin metabolites exhibiting considerable abundances in post-administration rat urine samples were detected, which might contribute to an improved sensitivity, specificity, and detection window in case of human sports drug testing programs. Further, the intact drugs were implemented into World Anti-Doping Agency-compliant initial testing (limits of detection 0.02-0.60 ng/ml) and confirmation procedures (limits of identification 0.18-0.89 ng/ml) for human urine and blood matrices. The obtained results allow extension of the test spectrum of doping agents in multitarget screening assays for growth hormone-releasing factors from human urine.