The function of<unk>  in adult humans is unknown.<unk>  is the most abundant plasma protein found in the human fetus. Maternal plasma levels peak near the end of the first trimester, and begin decreasing prenatally at that time, then decrease rapidly after birth. Normal adult levels in the newborn are usually reached by the age of 8 to 12 months. While the function in humans is unknown, in rodents it binds estradiol to prevent the transport of this hormone across the placenta to the fetus. The main function of this is to prevent the virilization of female fetuses. As human<unk>  does not bind estrogen, its function in humans is less clear. The rodent<unk>  system can be overridden with massive injections of estrogen, which overwhelm the<unk>  system and will masculinize the fetus. The masculinizing effect of estrogens may seem counter-intuitive since estrogens are critical for the proper development of female secondary characteristics during puberty. However, this is not the case prenatally. Gonadal hormones from the testes, such as testosterone and anti-Müllerian hormone, are required to cause development of a phenotypic male. Without these hormones, the fetus will develop into a phenotypic female even if genetically XY. The conversion of testosterone into estradiol by aromatase in many tissues may be an important step in masculinization of that tissue. Masculinization of the brain is thought to occur both by conversion of testosterone into estradiol by aromatase, but also by de novo synthesis of estrogens within the brain. Thus,<unk>  may protect the fetus from maternal estradiol that would otherwise have a masculinizing effect on the fetus, but its exact role is still controversial.
Alpha-fetoprotein
Mammaglobin
Carcinoembryonic antigen
Carcinoembryonic antigen peptide-1
AFP-L3
Prostate-specific antigen
CA19-9
CA 15-3