GIP (Glucose-Dependent Insulinotropic Polypeptide)
The second incretin hormone — tirzepatide's additional target — involved in insulin response and fat-tissue energy handling.
GIP is GLP-1's older, less famous sibling: the first incretin discovered, released from the upper intestine when food arrives, and responsible for a large share of the insulin response to meals. It also signals directly to fat tissue, influencing how energy is buffered and stored, and appears to act in the brain in ways still being mapped.
For years GIP was considered a dead end for obesity — early logic even suggested blocking it. Tirzepatide flipped the script: adding GIP agonism to GLP-1 produced larger weight loss than GLP-1 alone, with some evidence the combination also tempers nausea. When you read "dual-action" on a tirzepatide page, GIP is the second action.
This glossary entry is general information, not medical advice, and is written to be consistent with FDA prescribing information and primary trial publications as of its last review. Always consult a licensed healthcare provider for personal medical decisions.
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