It is a very well documented fact that as males age, serum Testosterone levels will decline. What is interesting to note, however, is that in many cases, LH levels will for the most part remain unchanged while Testosterone levels decline and low Testosterone is associated with negative alterations in body composition, energy levels, muscle strength and mass, sexual, physical, and cognitive functions as well as mood  . The same studies that have determined this have also determined that the age-related low Testosterone in the presence of increasing or unchanged serum Testosterone levels demonstrates that this is a result of the aging of the Leydig cells of the testes. The Leydig cells have undergone, due to the aging process, desensitization to LH stimulation whereby now their response to LH has diminished substantially. This is one such cause for low Testosterone in those that suffer from andropause, and is perhaps the most common cause. It is also one of the causes of which various treatments for this particular cause of low Testosterone will not work (this will be explained shortly). In any case, it is very evident that the frailty commonly displayed by aging men is resultant of these declines in endogenously manufactured androgens, as it is well known that this decline in Testosterone is a key contributor to sarcopaenia (loss of muscle mass and strength), which is a key sign of increased frailty whereby TRT (Testosterone replacement therapy) has been suggested as a treatment for this 
The partition coefficient of the ester in question is important because is effects how long the drug itself stays in the system. If the testosterone transfers too quickly from the oil to the blood, the result is a sudden spike in testosterone which then rapidly drops once the dose has been used up. In the example of free testosterone injected into the muscle from a water suspension (as in Aquiviron, mentioned above), the testosterone is essentially immediately available to the bloodstream due to its low partition coefficient, and thus there is an immediate spike of testosterone which is used up quickly in the body.