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Growth hormone axis

Macimorelin

Also called Macrilen, AEZS-130, EP-1572

Macimorelin is an oral ghrelin-like drug used as a one-time test for growth hormone deficiency in adults. A patient drinks a dose, and blood is drawn to see how much growth hormone the pituitary releases. It is FDA-approved as Macrilen for diagnosis only, not treatment.

FDA-approvedApproved by the FDA for at least one use after large human trials.

All printable flashcards

Drawn from its published sequence: 3 residues, one bead each.

Overview

Macimorelin is an oral ghrelin-like drug used as a one-time test for growth hormone deficiency in adults. A patient drinks a dose, and blood is drawn to see how much growth hormone the pituitary releases. It is FDA-approved as Macrilen for diagnosis only, not treatment.

How it works

Established: activates the ghrelin receptor (GHS-R1a) in the pituitary and hypothalamus, causing growth hormone release. A low GH response after a standard dose suggests adult GH deficiency.

What research shows

  • Approved for diagnosing adult GH deficiency; a peak stimulated GH level below 2.8 ng/mL confirms the diagnosis (label).

Doses studied in people

Study or labelDose usedSource
FDA label, Macrilen (diagnosis of adult GH deficiency)Single oral dose of 0.5 mg/kg (as a drink) after fasting at least 8 hours; blood GH measured at 30, 45, 60 and 90 minutes1

Used once, as a diagnostic test only; it is not a treatment.

Read this first: these are the amounts given to participants in published studies or written on official prescribing labels, reported for reference. They are not recommendations. Trial doses were chosen for specific patients under medical supervision, and a dose that is safe in one person can be harmful in another.

Safety

  • Label warning: raises the corrected QT interval by about 11 msec; avoid other QT-prolonging drugs.
  • Strong CYP3A4 inducers can cause false-positive results; recent-onset hypothalamic disease can cause false negatives (label).
  • Most common side effects in 154 adults were mild: taste change 4.5%; dizziness, headache and fatigue 3.9% each; nausea and hunger 3.2% each (label).

Report side effects of any drug or product to the FDA through MedWatch. For a possible poisoning in the US, call Poison Control at 1-800-222-1222.

History

Developed by Aeterna Zentaris. FDA approved Macrilen (NDA 205598) on December 20, 2017 as the first oral test for adult growth hormone deficiency.

Common questions

Is macimorelin FDA-approved?

Yes. FDA approved it as Macrilen on December 20, 2017, to help diagnose growth hormone deficiency in adults 4. It is a one-time test, not a treatment 1.

How is the test given?

Per the label, the patient fasts at least 8 hours, drinks a single dose of 0.5 mg/kg, and has blood growth hormone measured at 30, 45, 60 and 90 minutes 1. This is the label's test procedure, not a treatment dose.

What result points to growth hormone deficiency?

A peak growth hormone level below 2.8 ng/mL after the dose confirms adult growth hormone deficiency, according to the label 1.

What are the side effects?

In 154 adults, side effects were mostly mild, such as taste change (4.5%) and dizziness, headache and fatigue (3.9% each) 1. The label warns it lengthens the QT interval, a heart rhythm measure, by about 11 msec, so other QT-prolonging drugs should be avoided 1.

Can other drugs affect the test result?

Yes. Strong CYP3A4 inducers (drugs that speed up the liver's breakdown of other drugs) can cause false-positive results, and recent-onset hypothalamic disease can cause false negatives 1.

Is macimorelin banned in sport?

Yes. WADA prohibits it at all times and names macimorelin among growth hormone secretagogues 2.

Related compounds

Growth hormone axisLate-stage trialsFlashcard

MK-677 (Ibutamoren)

Ibutamoren mesylate · MK-0677

MK-677 (ibutamoren) is a pill, not a peptide, that copies ghrelin to raise growth hormone and IGF-1.

Growth hormone axisEarly human dataFlashcard

Ipamorelin

Ipamorelin acetate · NNC 26-0161

Ipamorelin is a small lab-made peptide (five building blocks) that copies the hunger hormone ghrelin to make the pituitary release growth hormone.

Growth hormone axisEarly human dataFlashcard

GHRP-2

Pralmorelin · KP-102

GHRP-2 is a small synthetic peptide that strongly triggers growth hormone release by acting on the ghrelin receptor.

Sources

  1. MACRILEN (macimorelin) prescribing information, revised 2/2026 (Drugs.com mirror of FDA label) FDA label
  2. WADA 2026 Prohibited List (in force 1 January 2026) Regulatory
  3. FDA: Bulk Drug Substances Nominated for Use in Compounding Under Section 503A (categories list, updated May 14, 2026) Regulatory
  4. Macrilen FDA approval history (Drugs.com) Regulatory

Last reviewed 2026-10-25 · How we research · Found an error? See our corrections policy.