Here's what our good Dr. Crisler has to say about both in his epic paper TRT: A recipe for Success. It's a bit dated now so keep that in mind, like having to go to Doc office to get IM injections...that's all done at home now. Nevertheless, the basic principals are the same.
TESTOSTERONE GELS AND CREAMS
The only way to go, in my professional opinion, if physician and patient agree on a transdermal (TD) delivery system. Or TRT at all. As I have gained knowledge and experience, my position is now that TD's are vastly superior to other modalities in TRT medicine. They are easy to apply, usually well absorbed, and rapidly establish stable serum androgen levels (by the end of the third day). I recommend all practitioners first try a testosterone gel for their TRT patients. Gels are better than creams, as I want the rapid T uptake into the dermal layer, which serves as reservoir for distribution throughout the day. Men do better on lower serum T levels on TD's than IM.
The constant variability of serum androgens provided by T gels mimic the hormones of a young man; the stable daily level provided by T injections mimic the hormones of an old man; those of implantable pellets mimic the hormones of no one. Entropic hormone levels are part and parcel of the process of youth.
Much is made of the risk posed by accidental transferal of testosterone to others, such as children or sexual partners. Simply covering with a T-shirt has been shown to block transfer of the hormone. The testosterone sinks into the skin within an hour. One may shower, or even swim, without worry, usually after four hours. I remind my patients most of us have neither the time, nor the opportunity, for romance until evening (given the usual early morning application), and a quick shower is always nice for a gentleman to “freshen up” prior to same.
Gels and creams, like all transdermal delivery systems, provide a greater boost in DHT levels, compared to injectable testosterone preparations. As DHT is responsible for all the things of manhood--literally, AllThingsMale--the transdermals are better at treating sexual dysfunction than are injectables. However, issues of hair loss (which I treat with a compounded topical DHT blocking mixture) and possible prostate morbidity (a contentiously debatable point, to be sure, but resolved in the negative to my mind) then come into play. This might be a good time to mention I vehemently oppose adding finasteride or similar medication.
To end the debate on this topic, transdermal T gels/creams are more likely to elevate estrogen than injections, as long as the shots are properly administered once per week. That is because aromatase lives in the skin, along with higher concentrations of 5-AR, which converts T to E. Even so, the benefits of TD TRT outweigh the weekly convenience of shots.
Some have reported an increase in hair growth over the application area(s). All physicians who administer TRT must be prepared to disappoint their patients at this time by pointing out, sadly, this same effect cannot be achieved upon the scalp.
TESTOSTERONE INJECTION
I'll start out by describing the drawbacks of IM testosterone. They are inconvenient for patients who do not wish to give themselves their own injections, as they must then make weekly trips to your office for same. Why IM test MUST be dosed weekly will be described in detail in another section. And this TRT modality represents hundreds of holes poked in their body over a lifetime. Some patients, as you well know, just hate shots (although I have noticed patients who had initially claimed this, but admitted, once they had come to enjoy the benefits of TRT, came to very much look forward to their shot day). And no doubt an invasive delivery system brings more risk than, for instance, a testosterone gel or cream (the best choice for TRT), although I have yet to hear of a single bad outcome from any of the tens of thousands of IM injections my patients have self-administered.
As a good and proper Osteopathic Physician, I am loath to introduce any substance to the body not absolutely necessary. Therefore the oil and preservative necessary to the injectable preparation are best avoided when possible, in my professional opinion.
When considering dosing of testosterone cypionate, it is important to remember that, due to the weight of the cypionate ester, a 100mg injection delivers, at best, 70mg of testosterone. This is important to keep in mind when comparing the effects of a 100mg weekly injection of test cyp to the 35mg total initial dose provided by Androgel/Testim 5gms QD over the same period.
HCG
Many practitioners consider this incredible hormone treatment of choice for hypogonadotropic (secondary) hypogonadism. Such certainly is intuitive, as supplementing with a LH analog indeed increases testosterone production in patients who do not concurrently suffer primary hypogonadism. But for some unexplained reason, while serum T levels may be adequately elevated, the patients simply do not report realization of the subjective benefits of TRT, when HCG is administered as sole TRT. You also run the risk of inducing LH insensitivity at higher dosages, and therefore may actually cause primary hypogonadism while attempting to treat secondary hypogonadism. HCG, especially at higher doses (defined as >500IU per shot), also dramatically increases aromatase activity, thus inappropriately elevating estrogens. Progesterone—a feminizing hormone in adult males—also elevates at those dosages. Personally, I recommend giving no more than 100IU of HCG per day, as starting dose. And please give it some time to work.
A real benefit of HCG is that it will prevent testicular atrophy. I do not think we should ignore the aesthetics of that consideration. Your patients will feel the same way.