Alpha fetoprotein is decreased in :
**Core Concept**
Alpha-fetoprotein (AFP) is a major plasma protein produced by the yolk sac and the fetal liver during fetal development. It serves as a marker for fetal development and is also used as a tumor marker for certain types of cancer, particularly hepatocellular carcinoma.
**Why the Correct Answer is Right**
The correct answer is associated with a condition where AFP levels are decreased. In this context, AFP is decreased in conditions that involve liver regeneration and increased cell turnover, which typically leads to a decrease in AFP production. This is because AFP is produced by the fetal liver, and conditions that cause liver injury or regeneration can affect AFP production.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because AFP is typically increased in conditions such as hepatocellular carcinoma, where the tumor produces AFP.
**Option B:** This option is incorrect because AFP is typically increased in conditions such as Down syndrome, where the fetus has an abnormal karyotype and increased AFP production.
**Option C:** This option is incorrect because AFP is typically increased in conditions such as fetal distress or intrauterine growth restriction, where the fetus has increased AFP production.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that AFP is a marker for fetal development and liver regeneration, and its levels can be affected by various conditions. Decreased AFP levels can be seen in conditions that involve liver injury or regeneration, such as liver cancer or cirrhosis.
**Correct Answer:** D. Liver regeneration (e.g. after liver transplantation)