Saturday, September 21, 2013

What is Alpha fetoprotein?


What is Alpha fetoprotein?

Alpha fetoprotein (α fetoprotein, AFP) is the most abundant plasma glycoprotein synthesized by the immature hepatic cells (liver cells) and yolk sac of the developing baby. Located on the chromosome 4, alpha fetoprotein is encoded by AFP gene.  AFP can be detected in the serum of the fetus as early as 28 days (4 weeks) of gestation.

Why Alpha fetoprotein is called so?
Bergstrand and Czar reported a new glycoprotein with α1-electrophoretic mobility, present in the serum of early human fetuses. It was not detectable in the adult human beings. So, this new glycoprotein was named as alpha fetoprotein or alpha1- fetoprotein (α1-fetoprotein).
AFP is also named as:
  • Alpha-1-fetoprotein
  • Alpha-fetoglobulin
  • Alpha fetal protein
  • Fetal form of serum albumin
The level of AFP declines rapidly after birth and reaches its normal levels till the age of one year.

What is the function of AFP?
The clear function of AFP is yet unknown; however, it is thought that α fetoprotein helps prevent masculinization of the female babies.

Why alpha fetoprotein tumour marker test is performed?
Alpha fetoprotein tumour marker test is performed to check the level of AFP in the mother’s blood to determine the fetal abnormalities. These defects may be chromosomal or structural defects. AFP test can be done to evaluate, diagnose or monitor the following conditions:
Neural tube defects
In neural tube defects, amniotic fluid and maternal serum shows raised/elevated levels of AFP. Neural defects are not associated with family or previous history but the low intake of folic acid during pregnancy.
  • Spina bifida
  • Miningocele
  • Miningomyelocele
  • Anencephaly

Chromosomal Problems
  • Down syndrome (trisomy 21)
  • Edwards syndrome (trisomy 18)
Congenital problems
  • Omphalocele
Cancers
AFP is rendered as a cancer tumour marker in the following cancers:
  •    Hepatocellular carcinoma- more than 500 ng/ml of AFP suggests liver cancer. Its sensitivity for hepatocellular carcinoma is 60 percent
  • Testicular carcinoma
  • Ovarian carcinoma
  • Stomach cancer
  • Pancreatic carcinoma
  • Certain brain tumours
  • Hodgkin disease
  • Lymphoma
In a nutshell, AFP is an important test to evaluate, diagnose or monitor neural tube defects, chromosomal defects, congenital problems and certain cancers (especially liver testicular and ovarian cancers).


Keywords: Alpha fetoprotein cancer marker, α fetoprotein, AFP, Glycoprotein, Alpha fetoprotein tumour marker test, Neural tube defects, Chromosomal problems, Hepatocellular carcinoma,

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