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.
Ellerby et al demonstrated that caspases, or "cysteine protease cell-death executioners", may act on the gene product (ie, androgen-receptor protein) resulting from the trinucleotide-repeat expansions, which act as substrates. Caspase cleavage affects proteins with the abnormal expanded polyglutamine tracts, resulting in cell death. Ellerby et al concluded that caspase cleavage is an important step in cytotoxicity (ie, neuronal cell death). [ 40 ] High circulating levels of androgens in men might precipitate the motor neuron degeneration observed in KD. [ 41 ] Ranganathan et al have shown that the mutant protein may affect mitochondrial function. [ 42 ]
As a mitochondrial P450 system, P450c11 is dependent on two electron transfer proteins, adrenodoxin reductase and adrenodoxin that transfer 2 electrons from NADPH to the P450 for each monooxygenase reaction catalyzed by the enzyme. In most respects this process of electron transfer appears similar to that of P450scc system that catalyzes cholesterol side chain cleavage.  Similar to P450scc the process of electrons transfer is leaky leading to superoxide production. The rate of electron leakage during metabolism depends on the functional groups of the steroid substrate.