AFP is a 68kD plasma protein found in fetuses over four weeks old, produced by the yolk sac and the fetal liver, with the highest concentration reached during the 12th to 16th week of gestation. It binds and transports various ligands such as bilirubin, fatty acids, steroids, heavy metals and various drugs. After birth, plasma levels drop to trace amounts in healthy adults.
Elevated AFP levels are indicative of certain cancers, particularly hepatocellular carcinoma, cancer of the testes or ovaries or a malignant teratoma. During pregnancy increased levels of AFP may indicate neural tube defects such as spina bifida, while decreased levels could indicate Down