Mechanisms of action
Levonorgestrel is a progestogen, i.e. a progesterone receptor agonist. The hormonal IUDs primary mechanism of action is to prevent fertilization. The levonorgestrel intrauterine system has several contraceptive effects, although thickening of the cervical mucus appears to be the primary effect. Other effects include making the inside of the uterus become fatal to sperm and thinning of the endometrial lining, but this is not the usual function.Ovulation is not inhibited in all cases.Numerous studies have demonstrated that IUDs primarily prevent fertilization, not implantation. In one experiment involving tubal flushing, fertilized eggs were found in half of women not using contraception, but no fertilized eggs were found in women using IUDs. IUDs also decrease the risk of ectopic pregnancy, which further implies that IUDs prevent fertilization. History
Hormonal IUDs were developed in the 1970s following the development of the copper IUD in the 1960s and 1970s. Dr. Antonio Scommenga, working at the Michael Reese Hospital in Chicago, discovered that administering progesterone inside the uterus could have contraceptive benefits. With knowledge of Scommegnas work, a Finnish doctor, Jouni Valter Tapani Luukkainen, created the T-shaped IUD that released progesterone, marketed as the Progestasert System in 1976. This IUD had a short, 1-year lifespan and never achieved widespread popularity.
In anatomy, the precordium or praecordium is the portion of the body over the heart and lower chest.Defined anatomically, it is the area of the anterior chest wall over the heart. It is therefore usually on the left side, except in conditions like dextrocardia, where the individuals heart is on the right side. In such a case, the precordium is on the right side as well. The precordium is naturally a cardiac area of dullness. During examination of the chest, the percussion note will therefore be dull. In fact, this area only gives a resonant percussion note in hyperinflation, emphysema or tension pneumothorax. Precordial chest pain can be an indication of a variety of illnesses, including costochondritis and viral pericarditis. See also
Precordial thump
Precordial examination
Commotio cordis
Hyperdynamic precordium
Precordial catch syndrome


== References ==