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 
Fluid and electrolyte disturbances: Retention of sodium, chloride, water, potassium, calcium, and inorganic phosphates.
Gastrointestinal: Nausea, cholestatic jaundice, alterations in liver function tests, rarely hepatocellular neoplasms and peliosis hepatis (see WARNINGS ).
Hematologic: Suppression of clotting factors II, V, VII, and X, bleeding in patients on concomitant anticoagulant therapy, and polycythemia.
Nervous system: Increased or decreased libido, headache, anxiety, depression, and generalized paresthesia.
Allergic: Hypersensitivity, including skin manifestations and anaphylactoid reactions.
Vascular Disorders: venous thromboembolism
Miscellaneous: Inflammation and pain at the site of intramuscular injection.