Glossary

Every term you need to read the research on retatrutide and the GLP-1 class — mechanism, trials, pharmacokinetics, FDA process, side effects.

ACHIEVE: Eli Lilly's Phase 3 trial program for orforglipron (Foundayo) in type 2 diabetes.
Agonist: A molecule that binds to and activates a receptor. Opposite of an antagonist, which blocks a receptor.
Amylin: A hormone co-released with insulin from the pancreas after meals. It slows gastric emptying and reduces appetite — a different pathway from GLP-1. Cagrilintide is an amylin analog. More →
ATTAIN: Eli Lilly's Phase 3 trial program for orforglipron (Foundayo) in obesity. ATTAIN-1 read out 12.4% weight loss at 72 weeks.
BLA (Biologics License Application): FDA application path for biologic drugs (including peptides like retatrutide). Equivalent to an NDA for small-molecule drugs.
CagriSema: Novo Nordisk's once-weekly combination of cagrilintide (amylin) and semaglutide (GLP-1). Phase 3 weight loss: 20.4% at 68 weeks. NDA filed December 2025. More →
Dose titration: Gradually increasing a drug dose over weeks to minimize side effects. GLP-1 drugs are always titrated — jumping straight to the target dose causes severe nausea.
Dual agonist: A single molecule that activates two different receptors. Tirzepatide (GLP-1 + GIP) and survodutide (GLP-1 + glucagon) are dual agonists.
Dysesthesia: An abnormal skin sensation — tingling, prickling, or burning. Reported at the 12 mg dose in retatrutide's Phase 2 trial.
FDA (Food and Drug Administration): The US agency that regulates drug approvals. A drug must be FDA-approved to be legally sold and prescribed in the United States.
Foundayo: Brand name for orforglipron, Eli Lilly's oral GLP-1 pill. FDA-approved April 2026 — the first non-peptide oral GLP-1 agonist. More →
GIP (Glucose-Dependent Insulinotropic Polypeptide): An incretin hormone. Activating its receptor amplifies insulin release after meals and may modulate fat metabolism. Tirzepatide was the first drug to target GIP alongside GLP-1.
GLP-1 (Glucagon-Like Peptide-1): A gut hormone that signals satiety and triggers insulin release. Semaglutide, liraglutide, and the oral orforglipron are GLP-1 receptor agonists. More →
GLP-3: An informal nickname for retatrutide — not a scientifically accurate term. Retatrutide activates three receptors (GLP-1 + GIP + glucagon); there is no actual "GLP-3" hormone. More →
Glucagon: A pancreatic hormone that raises blood sugar by signaling the liver to release glucose. At the glucagon receptor, activation also increases energy expenditure and fat breakdown — which is why GLP-1/glucagon dual agonists can drive meaningful weight loss.
Grey market: Sale of a drug or peptide outside the regulated prescription system. Often via online "research use only" vendors. Risks include contamination, mislabeled dose, and counterfeit compounds. More →
HbA1c: Glycated hemoglobin — a blood-glucose average over ~3 months. The primary efficacy endpoint for type 2 diabetes trials.
Incretin: A gut hormone released after eating that triggers insulin secretion. GLP-1 and GIP are incretins; drugs that mimic them are called incretin mimetics.
MACE (Major Adverse Cardiovascular Events): A composite endpoint in cardiovascular outcomes trials — typically cardiovascular death, non-fatal heart attack, and non-fatal stroke. TRIUMPH-5 uses MACE as its primary endpoint.
MASH (Metabolic dysfunction-Associated Steatohepatitis): The updated name for NASH — a liver disease where fat accumulation drives inflammation and fibrosis. Retatrutide, survodutide, and pemvidutide all have MASH programs. More →
MASLD (Metabolic dysfunction-Associated Steatotic Liver Disease): The updated name for NAFLD — fatty liver without inflammation. The "upstream" stage of MASH. More →
Microdosing: Using sub-therapeutic doses of a GLP-1 drug for metabolic or appetite effects without targeting maximal weight loss. Not studied in registration trials. More →
NDA (New Drug Application): The FDA application for small-molecule drug approval. The equivalent for peptides and biologics is a BLA.
Orforglipron: Eli Lilly's oral GLP-1 pill — a non-peptide small molecule. Brand name: Foundayo. FDA-approved April 2026. More →
Pharmacokinetics (PK): How a drug moves through the body — absorption, distribution, metabolism, and elimination. Retatrutide's long half-life is what enables once-weekly dosing. More →
Phase 1 / 2 / 3: Clinical trial phases. Phase 1 establishes safety in healthy volunteers; Phase 2 tests efficacy at different doses in the target population; Phase 3 is the large pivotal trial that supports regulatory approval. More →
REDEFINE: Novo Nordisk's Phase 3 trial program for CagriSema. REDEFINE 1 showed 20.4% weight loss at 68 weeks. More →
Retatrutide: Eli Lilly's investigational triple-agonist weight loss drug. Development code LY3437943. Activates GLP-1, GIP, and glucagon receptors. Phase 3 ongoing under the TRIUMPH program. More →
Semaglutide: A GLP-1 receptor agonist. Sold as Wegovy (weight loss), Ozempic (diabetes), and Rybelsus (oral tablet for diabetes). Novo Nordisk.
STEP: Novo Nordisk's Phase 3 trial program for semaglutide in obesity. STEP trials established semaglutide's ~15% weight loss profile.
SURMOUNT: Eli Lilly's Phase 3 trial program for tirzepatide in obesity. SURMOUNT-5 was the first head-to-head vs semaglutide.
SURPASS: Eli Lilly's Phase 3 trial program for tirzepatide in type 2 diabetes.
Telogen effluvium: Temporary hair shedding triggered by a stressor — rapid weight loss, illness, surgery. The mechanism behind hair loss seen in GLP-1 users. Usually reversible. More →
Tirzepatide: A dual GLP-1 / GIP receptor agonist. Sold as Zepbound (weight loss) and Mounjaro (diabetes). Eli Lilly.
Triple agonist: A single molecule that activates three different receptors. Retatrutide is currently the only triple agonist in Phase 3 trials, targeting GLP-1, GIP, and glucagon. More →
TRIUMPH: Eli Lilly's Phase 3 trial program for retatrutide. Eight trials (TRIUMPH-1 through TRIUMPH-6 plus TRIUMPH-MASLD and low back pain studies), ~5,800 participants total. More →
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