What does alpha-fetoprotein mean?

AFP is a glycoprotein. AFP in normal adult serum

1. AFP is a glycoprotein. Under normal circumstances, this protein mainly comes from the liver cells of the embryo. AFP disappears from the blood about two weeks after the fetus is born. Therefore, the AFP content in the serum of normal adults is less than 20 micrograms/liter.

2. Alpha-fetoprotein is mainly synthesized in the fetal liver, with a molecular weight of 69,000. At 13 weeks of fetal development, AFP accounts for 1/3 of the total plasma protein. It reaches its peak at 30 weeks of gestation and then gradually decreases. The plasma concentration at birth is about 1% of the peak, about 40 mg/L, and is close to the adult level (less than 30 μg/L) at one year old.

3. Alpha-fetoprotein AFP in maternal amniotic fluid or maternal plasma can be used for prenatal fetal monitoring. For example, in cases of neural tube defects, spina bifida, anencephaly, etc., AFP can enter the amniotic fluid through the open neural tube and cause its content in the amniotic fluid to increase significantly. Congenital defects such as fetal death in the uterine cavity and teratoma may also cause an increase in AFP in the amniotic fluid. AFP can partially enter the maternal blood circulation through the amniotic fluid. In 85% of mothers with spina bifida and anencephaly, plasma AFP can be seen to be elevated at 16-18 weeks of gestation and has diagnostic value, but it must be combined with clinical experience to avoid false positive errors.

4. In adults, AFP can be elevated in the serum of about 80% of liver cancer patients, and the AFP positivity rate in germ cell tumors is 50%. Patients with other gastrointestinal tumors such as pancreatic cancer, lung cancer, and liver cirrhosis may also experience varying degrees of increase.

5. However, when liver cells become cancerous, they regain the ability to produce this protein, and as the disease worsens, its content in the serum will increase sharply. AFP becomes a specific clinical indicator for diagnosing primary liver cancer.

6. In the past, it has been considered a specific tumor marker for diagnosing primary liver cancer, and it plays a role in establishing diagnosis, early diagnosis, and differential diagnosis. However, a large number of clinical studies have found that some patients with cirrhosis will have AFP levels of over 1,000 for a long time, but will show no signs of liver cancer for many years; at the same time, it has been found that about 20% of patients with advanced liver cancer have AFP levels not exceeding 10 until their death.