Macimorelin (also known as ARD-07, EP-1572, and JMV 1843) is a synthetic peptidomimetic growth hormone secretagogue. It is a potent and selective agonist of the ghrelin/growth hormone secretagogue receptor (GHSR). Structurally, it is a modified peptide designed for enhanced stability and oral bioavailability compared to the endogenous hormone ghrelin. The primary and established application of Macimorelin is in the field of clinical diagnostics. It is approved as a diagnostic agent (brand name Macrilen) for the evaluation of adult growth hormone deficiency (AGHD). The drug stimulates the pituitary gland to release growth hormone, and the resulting serum growth hormone levels are measured to assess pituitary function. This provides a safe and reliable alternative to the traditional insulin tolerance test. As a diagnostic pharmaceutical agent with a specific and regulated medical use, Macimorelin is classified as an active pharmaceutical ingredient (API). Its peptidomimetic nature also places it within the broader category of bioactive peptides used in life science research and therapeutic development.