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Oral Estrogen First-Pass Effect

Meaning

The Oral Estrogen First-Pass Effect describes the extensive metabolism of orally administered estrogen by the liver immediately following its absorption from the gastrointestinal tract and prior to its entry into the systemic circulation. This metabolic phenomenon significantly reduces the bioavailability of the active hormone and results in a higher concentration of estrogen metabolites, which can have distinct biological effects. Clinically, this effect is associated with altered hepatic protein synthesis, including increased production of clotting factors and Sex Hormone-Binding Globulin (SHBG). It is a key pharmacological consideration when choosing a route of hormone administration.