What hormone is primarily responsible for keeping the ductus arteriosus open?

The hormone that primarily keeps the ductus arteriosus open is prostaglandin. During fetal development, the ductus arteriosus connects the pulmonary artery to the aorta, allowing blood to bypass the lungs, which are not yet in use. Prostaglandins, especially prostaglandin E1, play a crucial role in maintaining the patency of this artery. In the fetus, prostaglandins are produced by the placenta and the ductus arteriosus itself, helping to keep it open and ensuring proper blood flow during a time when the lungs are filled with fluid and not yet functioning for gas exchange.

The other hormones listed do not have this specific role in maintaining the ductus arteriosus. Estrogen is primarily involved in the regulation of female reproductive functions and does not directly affect the ductus arteriosus. Oxytocin primarily triggers labor contractions and is not involved in maintaining ductus patency. Progesterone plays a vital role in pregnancy maintenance but does not impact the ductus arteriosus directly. By understanding the unique functions of these hormones, one can appreciate why prostaglandin is critical in keeping the ductus arteriosus open during fetal life.