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.
Microbial catabolism of phytosterol side chains yields C-19 steroids, C-22 steroids, and 17-ketosteroids (. precursors to adrenocortical hormones and contraceptives ).     The addition and modification of functional groups is key when producing the wide variety of medications available within this chemical classification. These modifications are performed using conventional organic synthesis and/or biotransformation techniques.  
The third SARM you can take solo or add to an entire regime of SARMs, including the other two SARMs above, is LGD4033 . It was developed to treat muscle wasting often associated with cancer , as well as age-related muscle-loss. It’s said to be similar to testosterone with the therapeutic benefits, but safer to use than testosterone. Several research trials show that use of LGD4033 increases lean body mass while decreasing body fat. It has the potential to offer healing, increase strength, and it is one of the better known SARMs for increasing drive, erections and sex drive.