Testosterone has different effects on various organs. It causes z. As "male sex hormone" the formation of the male phenotype, is responsible for growth (especially building muscle mass and fat storage) and ensures sperm production.
Testosterone, bound to a protein, is also transported to many other target organs, which have receptors for this hormone. The transport protein is called Sexual Hormone-binding Globulin (SHBG).
In the body, part of the testosterone in the target cells is metabolized by the enzyme steroid-5α-reductase (SRD5) to the biologically even more active dihydrotestosterone (DHT).
Outside the gender organs, the hormone promotes the growth of body hair and the beard hair (but not headset hair, see also hair loss) and has an anabolic, that is, muscle building, effect. Furthermore, testosterone reinforces cartilage and bone nation, similar to thyroxine. A high testosterone mirror promotes the emergence or increase sexual desire (libido) and generally drive, stamina and "life" as well as dominant and aggressive behaviors. Finally, by testosterone effect, it comes to a propagation of red blood cells (erythrocytes) by stimulating the release of erythropoetin in the kidney and activation of the bone marrow.