Progesterone controls the intracellular Ca2+
concentration and, thereby, the swimming behaviour of human sperm - this has been known for 25 years. However, the mechanism of action of the female sex hormone in sperm has remained mysterious and highly controversial. Researchers from the research center caesar in Bonn have now solved this long standing mystery: Progesterone directly opens sperm-specific CatSper (cation channel of sperm) Ca2+
channels located in the membrane of the sperm´s tail.