UPDATES:
(August 21st, 2006): I've been really busy and haven't been able to work on much lately. The site will be redesigned in a couple weeks and I'll try and have the new feature up as well.
(March 5th, 2006): There is going to be a huge update soon. I'm currently researching and developing a graphing system to display total testosterone levels relative to the amount of esterified testosterone injected. Stay tuned.
(February 6th, 2006): I've replaced the data set with a graph to allow for better understanding of the results
(September 1st, 2005): We've recently adjusted the half-lives to more accurately represent their true values. Consult the link below for details concerning our reasoning.
Why the hell does it tell me to start my PCT so late?
That is a good question as I wondered this the very first time I calculated one of my cycles. The build-up of exogenous(injected) testosterone causes a back-log of testosterone waiting to be de-esterified. The more you increase your dosage and/or dosing frequency, the longer it is going to take for the testosterone to clear your system.
Most people start their PCT too early and wonder why they feel like complete shit after finishing their PCT. It is because they began their PCT when they were still suppressed, possibly even finishing PCT while there was still exogenous testosterone suppressing natural production.
This is why you should stop any long esters by about 30 days before the end of your desired cycle length. You should then replace them with a short ester such as propionate so that you can gradually lower your testosterone levels down. Upon total discontinuation of injections, you can begin PCT in a relatively short timespan, as opposed to waiting several weeks had you not tapered with a short ester.
Why does it recommend starting PCT when esterfied levels hit 100mg?
It was determined from Table 2 of Testosterone dose-response relationships in healthy young men that 100mg results in a negligible change from base testosterone levels in men. So when esterified levels dropped below this point, endogenous testosterone production would resume.
*Note: The determined half-lives are only estimations. After performing a PCT calculation, an error margin of a few days should be considered. If you have any information that may be of aid to us, feel free to email us!
Propionate: 2 days
Reasoning: From analyzing graphs we determined that total testosterone levels began their drop 24 h after a single injection of 50mg testosterone propionate (1). Further analysis discovered levels were halved approximately 2 days after injection, and so that is the estimated half-life of the propionate ester.
Phenylpropionate: 3 days
Reasoning: Data revealed nandrolone phenylpropionate to have a little bit longer of a half-life than that of propionate (2). Although there have not been many studies done using the ester, it's estimated half-life is 3 days.
Isocaproate: 5 days
Reasoning: With a shorter ester than that of enanthate and longer than that of phenylpropionate, the isocaproate half-life is rougly estimated to have a 5 day half-life. This is based on the carbon composition of the ester alone as there exists very little known studies on this ester.
Enanthate: 7 days
Reasoning: From analyzing many graphs and data tables concerning the half-lives of testosterone enanthate(1, 4, 5), it was concluded that the half-life was measured to be about 7 days. We noted that weekly injections of 200mg TE resulted in a continual rise in total testosterone levels until it plateaued at 12 weeks (3). The total testosterone levels between the 8th and 12th week were not significantly different signifying that an estimated half-life of 7 days properly fit the calculated predictions for testosterone levels.
Cypionate: 7 days
Reasoning: Differing from enanthate by only 1 carbon atom, the cypionate ester has no noticeable changes in half-life from enanthate (1). Thus it shares the same, 7 days.
Decanoate: 9.5 days
Reasoning: Being 3 carbon atoms longer, this ester should have an extended half-life over enanthate. This is shown evidently in studies done on single-shot injections of Nandrolone Decanoate (3). The half-life varied from 7-12 days leaning more towards 12 days depending on injection site. We took the average of that which was 9.5.
Undecanoate: 34 days
Reasoning: From detailed graphs and also clinically calculated half-lifes in (1), the estimated half-life of the undecanoate is an impressive 34 days. Definitely not an ester to use for short cycles.
(1) Testosterone: Action, Deficiency, Substition
E. Nieschlag
Ch. 14.3, 405-435
(2) Pharmacokinetics and Pharmacodynamics of Nandrolone Esters in Oil Vehicle: Effects of Ester, Injection Site and Injection Volume (Mirror)
Charles F. Minto, Christopher Howe, Susan Wishart, Ann J. Conway and David J. Handelsman
J Pharmacol Exp Ther. Vol. 281, Issue 1, 93-102, 1997
(3) Comparison between testosterone enanthate-induced azoospermia and oligozoospermia in a male contraceptive study. II. Pharmacokinetics and pharmacodynamics of once weekly administration of testosterone enanthate (Mirror)
RA Anderson and FC Wu
Am J Physiol Endocrinol Metab, 1996; 81: 896 - 901
(4) Current Status of Testosterone Replacement Therapy in Men (Mirror)
Stephen J. Winters, MD
Arch Fam Med. 1999;8:257-263.
(5) Testosterone dose-response relationships in healthy young men (Mirror)
Shalender Bhasin, Linda Woodhouse, Richard Casaburi, Atam B. Singh, Dimple Bhasin, Nancy Berman, Xianghong Chen, Kevin E. Yarasheski, Lynne Magliano, Connie Dzekov, Jeanne Dzekov, Rachelle Bross, Jeffrey Phillips, Indrani Sinha-Hikim, Ruoquing Shen, and Thomas W. Storer
Am J Physiol Endocrinol Metab, Dec 2001; 281: 1172 - 1181.
The effects of exogenous testosterone on sexuality and mood of normal men (Mirror)
RA Anderson, J Bancroft and FC Wu
Am J Physiol Endocrinol Metab, 1992; 75: 1503 - 1507