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.
The side effects of Trenbolone do include those of an androgenic nature, which isn’t surprising when this steroid’s androgenicity is so greatly pronounced. The androgenic side effects of Trenbolone are highly dependent on genetics and can include acne in sensitive individuals, accelerated hair loss in those predisposed to male pattern baldness and body hair growth. If you are not predisposed to male pattern baldness there is no risk of hair loss, but Trenbolone is notorious for promoting hair loss in those who are predisposed. Keep in mind, you were going to lose your hair anyway, but the use of Trenbolone may speed it up. Acne is largely the same; only those who are sensitive are at risk; many men can easily use Trenbolone without issue.