I am on TRT via my general physician.I use 100mg cyp each week. My Doc wants to check my peak but both he/I have questions about true peak time. AACE(American assoc of clinical endocrinologist)says test peaks at approx 72hrs post injection. Test (Cyp) package insert states a half life of 7 days.
My last lab was 500(total) on the day of next injection(this would be lowest point before next dose). The obvious question is why doesn’t doc know. In docs defense he is a family pract in rural area. He has been very open and helpful so I am not going to knock him(even on the net). Sincere thanks for any help.
Sorry for this long post! Thanks for the info. Bushy, I was using the same logic with the difference being half life time as I only went with the pharmacology.
I would like to think my level was close to 1000 at peak and that the 500 was the true low point. A sure answer would be to have lab drawn each day between injections thus peak would show but, that ain’t a possibility.
Doc said I was likely supraphysio(above normal high)for a short time before declining. I’m hoping the true half life is 7 days as that sure makes my level look better. The 7 day half life would agree with AACE saying peak at 72 hours. Any help is appreciated!
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.
bushy[/quote]
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.