Hormone · FDA Approved
Macimorelin (Macrilen)
FDA-approved
01 · Overview
An orally active ghrelin mimetic and growth hormone secretagogue developed as a diagnostic agent for adult growth hormone deficiency (AGHD). Macimorelin acutely raises GH levels via the ghrelin receptor GHS-R1a, and the GH response to a single oral dose is used to help confirm or exclude AGHD (PMID 24834478).
It was developed as a simpler alternative to the insulin tolerance test, which is labor intensive, can cause severe hypoglycemia, and is contraindicated for some patients (PMID 29860473). The US product Macrilen (approved 2017) is now listed by the FDA as discontinued.
02 · Research summary & key findings
FDA-approved in December 2017 as Macrilen for diagnosis of AGHD; the product is currently listed as discontinued in the FDA database. In a phase 3 crossover trial versus the insulin tolerance test, macimorelin showed 87% sensitivity and 96% specificity at the 2.8 ng/mL GH cutoff, with 97% reproducibility on retesting (PMID 29860473). Post hoc analyses found that test performance was not meaningfully affected by age, BMI, or sex (PMID 33320108). A real-world study found GH values at 60 and 90 minutes were highly correlated and that obesity may affect classification in low pre-test probability patients (PMID 41793495). No serious adverse events were reported for macimorelin in the phase 3 trial (PMID 29860473).
03 · Regulatory status
Macimorelin (Macrilen) has received FDA approval and is available for clinical use under appropriate medical supervision. Consult a qualified healthcare provider for prescribing information.
Macimorelin (Macrilen) is an FDA-approved medicine prescribed for the conditions on its label. It is not part of our intake, so we do not propose protocols for it. If you think it may be relevant to you, talk to your own doctor. How to ask your doctor.
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04 · Administration routes
- Oral
References
- [1]The macimorelin-stimulated growth hormone test for adult growth hormone deficiency diagnosis Expert Rev Mol Diagn, 2014. PMID 24834478
- [2]Macimorelin as a Diagnostic Test for Adult GH Deficiency J Clin Endocrinol Metab, 2018. PMID 29860473
- [3]Sensitivity and specificity of the macimorelin test for diagnosis of AGHD Endocr Connect, 2021. PMID 33320108
- [4]Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency Pituitary, 2026. PMID 41793495
Primary literature
- PubMed: "Macimorelin"
Peer-reviewed literature indexed by the National Library of Medicine.
- ClinicalTrials.gov: "Macimorelin"
Registered interventional and observational studies, including status and phase.
- PubChem: "Macimorelin"
Chemical structure, molecular properties, and bioactivity data.
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