excretion

Last reviewed 01/2018

The half life of free sex steroids is very short. This is due to clearance by:

• tissue uptake and receptor binding
• inactivation by liver ready for excretion

Liver inactivation entails:

• oestrogens and androgens: conjugation with glucuronic or sulphuric acid
• progestogens: conversion to oestrogens or androgens before conjugation

The conjugated steroids may be secreted into urine or bile. Biliary excretion is accompanied by gastrointestinal reabsorption and faecal loss. Hence, the measurement of urinary sex steroid metabolites does not give an index of sex steroid production.