Multiple choice __________ hormone is formed by placenta during pregnancy. HCG hormone Progesterone Estrogen Thyroxine Reveal answer Fill a bubble to check yourself A Correct answer Explanation The hormone human chorionic gonadotropin (better known as HCG) is produced during pregnancy. It is made by cells that form the placenta, which nourishes the egg after it has been fertilized and becomes attached to the uterine wall.