Alpha-fetoprotein

Alpha-fetoprotein (AFP) is a protein predominantly synthesized in the fetal liver, yolk sac, and gastrointestinal tract. Its genetic expression is derived from the AFP gene located on the q arm of chromosome 4 (4q25).

AFP_prot

Structure

AFP is a glycoprotein consisting of 591 amino acids bound to a carbohydrate moiety.

Function

AFP acts as the fetal counterpart of serum albumin. Its high concentration in the fetal bloodstream gradually subsides, with typical adult levels reached between 8 to 12 months post-birth. While the AFP's specific purpose in adults remains speculative, its role in rodents offers some clarity. In rodents, AFP binds to estradiol to inhibit its placental transfer, thereby averting potential virilization of female fetuses. This function in humans, however, is less explicit since human AFP doesn't bind estrogen.

Serum levels

AFP concentrations in pregnant women can be assessed through urine since it is rapidly filtered from maternal blood by the kidneys. These levels naturally increase until approximately week 32 of gestation. For adults and children, normal AFP levels fall below 50, 10, or 5 ng/mL, depending on specific reports. It's crucial to recognize the naturally high AFP concentrations in infants post-birth, which typically return to standard levels within their first year.

Clinical significance

AFP measurements serve dual purposes:

• Prenatal Testing: Evaluating maternal blood or amniotic fluid AFP levels can screen for developmental abnormalities in the fetus, such as neural tube defects or aneuploidy.
• Tumor Biomarker: Elevated serum AFP levels can indicate the presence of specific tumors, making it a valuable biomarker for tracking disease progression.

Associated conditions

• Developmental Abnormalities:
  • Omphalocele
  • Gastroschisis
  • Neural tube defects
• Tumors:
  • Hepatocellular carcinoma
  • Metastatic liver disease
  • Nonseminomatous germ cell tumors
• Yolk sac tumor
  • Other Conditions:
  • Ataxia telangiectasia

Furthermore, a peptide known as AFPep, derived from AFP, has demonstrated potential anti-cancer properties.

See also

• Tumor marker
• AFP-L3
• Triple test
• Advanced maternal age
• AFP and AFP non-covalent complex as a drug

External links

• alpha-Fetoproteins at the US National Library of Medicine Medical Subject Headings (MeSH)