Figure 3.

Enterohepatic circulation of sex steroids and bile acids. 1) Sex steroids (S) are conjugated with glucuronide from uridine 5’-diphosphoglucuronic acid (UDP-GlcA) by liver enzymes. Bile acids (BAs) are synthesized and conjugated with glycine (Gly) or taurine (Tau) in the liver. 2) Sex steroid glucuronides (S-glucuronide) and primary bile acids are transported to the gallbladder and excreted into the small intestine via the bile duct. 3) Gut bacteria deconjugate S-glucuronide and transform BAs into secondary BAs or other BA metabolites. 4) S-glucuronides that are not deconjugated are excreted through the feces. 5) Secondary BAs, other BAs metabolites, and deconjugated sex steroids are primarily reabsorbed through the hepatic portal vein to the liver. Alternatively, they are excreted through feces or returned to circulation, to be reabsorbed by the liver or excreted through urine. Created with BioRender.com.