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.
As for the idea that letrozole won't help gyno "caused" by progesterone(or that AI's won't help that kind), that's bullshit. The basic biology of breast cancer and breast tumors (which is what gyno is...a benign breast tumor) indicates that estrogen contributes to its development, and that it is essentially estrogen dependant. Nearly all existing mammary tumor models in most species confirm this. Human models, animal studies, in vitro, in vkivo...you name it...it's estrogen, not progesterone. Estrogen grows the gyno, not progesterone. Concerning progesterone, actually, In some studies it actually has an inhibiting effect on breast cancer growth and tumor development.
I would very much like your opinion, and I will check with my Doc before I take anything. I am as active as I can be, no weight training or pumping iron for me, the damage to my shoulders, knees, back, and neck prevent any heavy lifting. I do walk approx. one mile everyday (1/8 of a mile at a time) and I do my best to stay active with projects around the house. I don’t eat junk foods, drink, or do illegal drugs, and I am also working with my Doc to reduce the number of meds I am on, but like I said, I need something that can help me kick start the weight loss.