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背景
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alpha-Fetoprotein (AFP), is albuminoid superfamily protein that is synthesized in the fetus primarily by the liver, yolk sac, and tissues of gastrointestinal origin. It is one of the earliest markers of the hepatocyte lineage. AFP acts as a carrier protein for steroids, bilirubin, fatty acids, retinoids, and flavonoids. In addition, it can exert immunosuppressive activity, regulate cell proliferation and apoptosis, initiate intracellular signaling, and contribute to cell invasion. Altered levels of both fetal and maternal AFP have been associated with hypothyroidism, autoimmune disorders, and heart defects. Low maternal serum AFP levels are associated with a higher incidence of Down syndrome, whereas higher levels are associated with spina bifida and anencephaly. Elevated AFP levels are also coincident with liver, stomach, and germ cell cancers.
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