Anastrozole has no harsh side effects. Actually, affecting estradiol, it can suppress the level of the good cholesterol (HDL). However, when compared to AI like letrozole, anastrozole is preferable. Letrozole has quite a few side effects, the most common of which is erectile dysfunction. Although estradiol is known as a female hormone, men still need it. Estradiol maintains hormonal balance, participates in a great number of physiological processes and helps to gain muscle mass and strength. Such potent AI as letrozole kills almost all estradiol, disrupting the hormonal balance and causing a number of side effects, such as erectile dysfunction, joint pain, bones fragility, unwellness, etc. Anastrozole acts more smoothly and does not kill all estradiol immediately, allowing you to more finely adjust the hormonal balance.
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.