Glossary Terms

The degradation of a compound in the gut and liver before it reaches the bloodstream — the main reason you

The compound has no FDA approval and no active clinical development in the US — it has not been formally

The compound is not yet approved but is under active investigation — it has been tested in humans in clinical

The compound has been fully approved by the FDA for human use — meaning it passed Phase III clinical trials

Administered from outside the body — whether injected, swallowed, or applied to skin.The distinction between endogenous and exogenous matters because

A ranking of research study types by how reliably they establish cause and effect — not all research is equally

The brown and black form of melanin — the protective pigment that gives skin its darker tones and shields DNA

A rare genetic disorder that makes sunlight excruciatingly painful — caused by a deficiency in a blood enzyme that leaves

A serious infection inside the eye that can cause permanent blindness — a known risk of intravitreal injection even when

Produced naturally inside the body — as opposed to something you’d administer from outside.Endogenous peptides (GLP-1, insulin, oxytocin, alpha-MSH) have