Abuse of anabolic steroids, however, can result in significant harm to the body. In humans, abuse can lead to coronary heart disease , sexual and reproductive disorders, immunodeficiencies , liver damage, stunted growth, aggressive behaviour , susceptibility to connective tissue injury, and (in females) irreversible masculinization. Similar side effects can occur in livestock and other animals. In horses , for example, anabolic steroids can cause liver damage and weakening of the tendons and can result in decreased testis size and sperm production in stallions and altered reproductive cycling in mares. Anabolic steroids are readily detected in urine and blood .
Testosterone can be administered parenterally , but it has more irregular prolonged absorption time and greater activity in muscle in enanthate , undecanoate , or cypionate ester form. These derivatives are hydrolyzed to release free testosterone at the site of injection; absorption rate (and thus injection schedule) varies among different esters, but medical injections are normally done anywhere between semi-weekly to once every 12 weeks. A more frequent schedule may be desirable in order to maintain a more constant level of hormone in the system.  Injectable steroids are typically administered into the muscle, not into the vein, to avoid sudden changes in the amount of the drug in the bloodstream. In addition, because estered testosterone is dissolved in oil, intravenous injection has the potential to cause a dangerous embolism (clot) in the bloodstream.