Macimorelin
Also known as: Macrilen®
An oral ghrelin receptor agonist FDA-approved as a diagnostic test for adult growth hormone deficiency. Macimorelin (Macrilen®) is the only approved oral GH stimulation test. It acts as a selective agonist of the ghrelin receptor (GHSR-1a), stimulating growth hormone release from the anterior pituitary gland. Administered as a single oral dose in a clinical setting after overnight fasting, with blood samples collected at baseline and 30, 45, and 60 minutes post-administration to assess GH secretory capacity.
Beginner Basics
Plain-English guide to Macimorelin
What it does
Macimorelin is an oral medication that triggers the body to release growth hormone so doctors can test whether someone's pituitary gland (a small gland in the brain) is making enough of it. Researchers use it as a diagnostic test to identify growth hormone deficiency in adults.
Typical dose
A single dose of 0.5 mg per kilogram of body weight (up to a maximum of 30 mg), taken by mouth as a tablet dissolved in water, typically in a doctor's office or clinical setting.
When to inject
In the morning after fasting (not eating) for at least 8 hours overnight, in a clinical setting where blood samples can be drawn at specific time points (baseline, then 30, 45, and 60 minutes after taking it).
Storage
Store the dry tablet at room temperature away from moisture until use. This is a single-dose diagnostic test administered only in clinical settings, so home storage is not typical.
First-timer tip
This is a diagnostic test, not a self-administered therapy-your doctor will give it to you in their office and monitor your response with blood tests, so there's no home injection technique to learn.
On This Page
Research Status
Extensive Clinical Data
For research purposes only. Not approved for human use. Not medical advice.
Research Areas
Side Effects
Occurs in approximately 10-15% of patients. Usually transient and resolves without intervention. May be reduced by ensuring patient remains fasting and seated during test.
Reported in 1-5% of patients, typically related to fasting state. Patient should remain seated or recumbent during testing. Resolves after test completion.
Occurs in 1-3% of patients. May be related to fasting or stress of diagnostic procedure. Typically self-resolving.
Expected pharmacological effect of ghrelin receptor agonism. Patient should remain fasting during the diagnostic test period (approximately 1 hour).
Macimorelin may transiently elevate cortisol levels. Not clinically significant in single-dose diagnostic use. Relevant for patients with adrenal insufficiency — consult with endocrinologist.
Reported in <1% of patients. Transient and self-resolving.
Rare but documented. Patient should be monitored during test. Contraindicated in patients with uncontrolled cardiac arrhythmias or acute coronary syndrome.
Allergic reactions including rash, urticaria, or angioedema are rare but possible. Discontinue immediately and seek medical attention if signs of anaphylaxis develop.
Dosing Reference
| Parameter | Value |
|---|---|
| Dose range | 0.5 mg |
Frequency, timing and route - members only | |
Research disclaimer
Figures drawn from published research literature and community logs. Not clinical recommendations. Consult a qualified professional. Research use only.
Reconstitution Guide
Do not use saline or bacteriostatic saline, use only bacteriostatic water for reconstitution
Do not shake the vial vigorously; gentle swirling prevents peptide degradation
Discard immediately if the solution appears cloudy, discolored, or contains visible particles
Use within 30 days of reconstitution when stored at 2-8°C
Do not freeze the reconstituted solution; freezing may denature the peptide
Use the PeptideVolt reconstitution calculator for your exact concentration
Molecular and Pharmacological Data
Macimorelin is a selective oral agonist of the ghrelin receptor (GHSR-1a) that stimulates growth hormone secretion from somatotroph cells in the anterior pituitary gland. By mimicking the action of endogenous ghrelin, macimorelin triggers GH release, allowing clinicians to assess the functional capacity of the GH axis in patients suspected of growth hormone deficiency. The magnitude of GH response to macimorelin administration serves as a diagnostic indicator of pituitary GH reserve.
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Recent Research
Neurophysin-I dynamics upon different pituitary provocation tests in healthy participants.
Facts and news about growth hormone replacement therapy in adults.
Real-world diagnostic performance of the macimorelin stimulation test in the diagnosis of adult growth hormone deficiency.
Source: PubMed / NCBI. Updated daily. Articles are listed for research reference only.
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View all peptidesResearch Use Only. All content on this page is provided for informational and educational purposes related to scientific research. Macimorelin is not approved for human use by the FDA or any equivalent regulatory body. This is not medical advice. Do not use any substance discussed here for therapeutic, diagnostic, or preventative purposes. Consult a qualified healthcare professional before making any health-related decisions. The Peptide Volt does not endorse the use of any research chemicals. 18+ only.