The placenta has long been thought to produce serotonin during pregnancy.
But in a new study, Yale researchers shatter the deep-rooted hypothesis - and show that the placenta doesn't produce serotonin but instead regulates its delivery to the embryo and fetus. They found that serotonin comes from the pregnant parent, with the placenta acting as a "serotonin shield" that controls how much reaches the embryo and fetus.
The findings, published in the journal Endocrinology, could offer critical insights into how a parent's serotonin levels might affect the development of their baby's body and brain, the researchers say.
"The placenta is in essence the 'serotonin shield' that regulates how much serotonin is ultimately delivered to the embryo and fetus, not the source of serotonin," said Harvey Kliman, a research scientist in the Department of Obstetrics, Gynecology, and Reproductive Sciences at Yale School of Medicine and corresponding author of the study. "Why does this matter? Because now we correctly know where this delivery is regulated."
Often called a "happiness hormone," serotonin regulates mood, so it's often associated with the brain. In reality, less than 5% of serotonin is made in the brain, with 95% of it made in the gut. But serotonin does more than just regulate mood. It's also a growth hormone. In the gut, it gets taken up by platelets and is delivered to parts of the body that need to grow, including in wound healing.
During pregnancy, serotonin also helps with growth: It travels into the placenta through a special protein known as the serotonin transporter (SERT) where it plays a critical role in the development of the embryo and fetus.
