So why doesn’t all the test hit the system after 12 days, ie when all the carbons have been removed from all the test? I can’t find a definitive answer, but I am assuming that much like any other chemical reaction, it doesn’t all take place at once due to enzyme concentration and other factors.
The reason all the testosterone doesn’t all become active at once is because Bushy explained it wrong (no offense, but I’m a bit of a chemist myself). Testosterone is bound to chain of carbon atoms (in most cases). This carbon-chain/testosterone combination is known as an ester. If the testosterone is not bound to anything it is known as free testosterone. Your body can only use free testosterone, and must cleave off the ester group (the carbon chain) to use the testosterone you inject into your body.
You happen to be using the cypionate ester, which was a eight carbon chain attached to it. The more carbons a steroid ester has the more soluble it is in oil. The more soluble the ester is the harder it will be to take it out of solution (not be dissolved in oil or, once injected into your body, body fat). Enzymes within your body remove the steroid esters from you fat and esterase enzyme cleaves off the carbon chain via hydrolysis. The end products in this reaction for testosterone cypionate would be free testosterone and cpyionic acid.
This is where Bushy was unsure; the carbon chain is cleaved off in its entirety. The reason the various testosteone esters have differing half-lives is due to their solubility in oil.
As far as determining peak serum concentrations, this can be found using the partition coefficient. Though I can’t remember how it’s done. I’ll try to look up some numbers and figure it out.