Mechanism of action.

The specific biochemical way a compound produces its effect.

Mechanism of action describes the specific molecular interaction through which a compound produces its biological effect: which receptor or enzyme it engages, what happens downstream of that engagement, and in which tissues. A well-specified mechanism is concrete and testable, for example that a compound is an agonist at the GLP-1 receptor, which increases glucose-dependent insulin secretion, slows gastric emptying, and acts on appetite centres in the brain. A vague mechanism, such as supports cellular repair or optimizes recovery pathways, is not a mechanism at all; it is a description of a hoped-for outcome with scientific vocabulary attached. Learning to tell these apart is probably the most transferable skill for reading peptide claims, because the specific version can be checked and the vague version cannot. Two further points are worth holding. Mechanism is frequently established in cells, so a confirmed mechanism tells you how a compound could work without telling you whether it does anything useful in a person. And several genuinely effective drugs were used for years before their mechanism was understood, so the reverse also holds: a well-described mechanism is not a substitute for outcome evidence, and outcome evidence does not require a fully mapped mechanism.