Alpha-Fetoprotein (AFP) is a protein that is normally produced by the fetal liver, yolk sac, and gastrointestinal tract during development.  It is typically present in high levels in the blood of the fetus and in the amniotic fluid.  AFP levels decrease rapidly after birth and are usually very low in healthy adults.

    In adults, elevated AFP levels can be a marker for certain types of cancers, particularly liver cancer (hepatocellular carcinoma), germ cell tumors (such as testicular cancer), and certain ovarian cancers.  It is used in diagnostic procedures, monitoring treatment response, and detecting cancer recurrence.