Gallsyrorna

Gallsyrorna, or bile acids, are steroid acids produced from cholesterol in the liver and are essential components of bile. They exist in primary forms, such as chenodeoxycholic acid and cholic acid, and can be modified by gut bacteria into secondary bile acids like deoxycholic and lithocholic acid. In the liver these acids are conjugated with the amino acids glycine or taurine, which increases their solubility and helps transport them in bile.

Bile acids are secreted into bile and stored in the gallbladder. When fatty foods enter the small intestine, bile is released into the duodenum to emulsify fats, facilitating digestion and absorption. After performing their digestive role, most bile acids are reabsorbed in the ileum and returned to the liver via the enterohepatic circulation, where they can be reused. A portion is excreted in feces, providing a route for cholesterol elimination.

Beyond digestion, bile acids act as signaling molecules, influencing metabolic pathways through receptors such as FXR and TGR5. This signaling can affect lipid, glucose, and energy metabolism, and may have implications for liver and metabolic diseases.

Clinical relevance includes changes in bile acid composition and flow in cholestasis, gallbladder disease, and liver disorders. Abnormal bile acid levels or patterns can aid diagnosis and monitoring. Therapeutically, certain bile acids or derivatives (for example ursodeoxycholic acid) are used to treat specific biliary disorders.