How testosterone shots work

There was recently a post on our forum OzGuys, where a member was refused assistance with their regular Sustanon injection.

The doctor refused to assist him and made some statement about Sustanon being synthetic and therefore harmful. The same doctor also said testosterone gel was made from all natural products and therefore better.

I want to clear up a few points about how the shots that most of us are on actually work. I am not a medic, but I am a research chemist. The following explanation is my best effort at explaining to someone who hasn’t studied any science.

The gel contains free testosterone (“Free” testosterone is simply testosterone that isn’t bound to anything – most of the testosterone in our bodies is bound to a protein called Sex Hormone Binding Globulin or SHBG if you see it on your bloodwork) . The injections contain testosterone esters, which are a simple derivative of testosterone, explained below. Sustanon250 contains 30 mg testosterone propionate, 60 mg testosterone isocaproate, 60 mg testosterone phenylpropionate and 100 mg testosterone decanoate. There is a total of 176 mg free testosterone in each ml (the other 74 mg are the ‘ester bits’).

Fig. 1 Chemical structure of Testosterone
Fig. 1 Chemical structure of Testosterone

As testosterone is not easily soluble in oil, they make an ester of it by tacking on (to the OH bit at the top of the picture above) some carbon chains (propionate = tiny, isocaproate = small, phenylpropionate = medium, decanoate = large – you can look up the structures of these on the patient information sheet that comes in the box, all that’s important though is the size) that increase the oil solubility of testosterone. This works because oils are basically long carbon chains and “like dissolves like”. The esters aren’t all that stable and once injected, they hydrolyse (the tacked on bit falls off), once this happens the free testosterone is no longer soluble in oil (but is soluble in water) and thus migrates to where water is – which happens to be your bloodstream – this is a good thing. The smaller the tacked on bit is, the faster it hydrolyses (breaks down in water). Propionate takes around 3-4 days to do this, isocaproate takes about 6 days, phenylpropionate takes 9-10 days and decanoate takes around fourteen days. The longer the time, the more spread out the peak from that particular ester is.

Overall, what happens looks roughly like the following graph:

Fig 2: Approximate Testosterone levels after a Sustanon250 injection
Fig 2: Approximate Testosterone levels after a Sustanon250 injection

So at four days after an injection, your total testosterone (T) level is made up of mainly T-propionate, but a little bit of T-isocaproate. At seven days, the T-propionate has pretty much gone, your T level is made up of mostly T-isocaproate but a fair bit of T-phenylpropionate and a tiny bit of T-decanoate. At twelve days nearly all the T-isocaproate has hydrolysed and your T level is mainly made up of T-phenylpropionate and T-decanoate. After about two weeks, T-decanoate is all that is left.

The ester bits and the oil are simply disposed of by your body.

Testosterone in the injections is modified (i.e., the modification is undone in your body), whereas the gel contains free testosterone, could be taken to mean that the gel is “more natural” but then the absorption enhancers in the gel certainly aren’t natural. Remember testosterone is poorly soluble in fat/oil? The absorption enhancers present in gel work by creating channels between fat cells for the testosterone to “burrow through” – not a very efficient process, which is why a 5mg patch actually contains 10x that. The absorption enhancers (the simplest one is ethanol – which is the alcohol in drinks) are also the main culprits in skin irritation.

The idea of taking one thing (in this case testosterone ester) into the body, when the actual drug is something else (in this case testosterone) is not new. Many drugs are converted to their active form once in they are put into the body. The stuff you take is called a pro-drug. Once the pro-drug is converted to its active form, it is a drug. For example, the well known cancer treatment cisplatin is a pro-drug.

The “more natural” mentality is pseudoscience, whether it is applied to pharmaceuticals or food. There are many forms of testosterone in your body. So ask yourself, is the protein bound hormone less natural than the free form? (both are naturally present). All that matters for your body, is that adequate androgenization (masculinising) is occurring, and that all other parameters (cholesterol etc) are in order. Of course, regardless of where you are in transition, it’s a good idea to get your GP to check your cholesterol every six months or so.

Another point the guy on the email discussion group was told by the medic was because Sustanon is synthetic, it destroys the natural testosterone that the body produces. This is mixing correct and incorrect science together (pseudoscience).

Firstly a chemical (be it a food additive or a drug or something else) is the same chemical, regardless of whether it was isolated from a natural source (a plant or an animal) or whether it was manufactured by chemists. Both the testosterone in the gel and the testosterone in the injections are manufactured the same way. The T in the injections has one extra step (taking on the ester bits) which is undone in your body.

It is true, that taking large amounts of exogenous (from outside the body) hormones will decrease natural hormone production, but not because they are synthetic.

When testosterone abusers (for example, bodybuilders who often take in excess of 1000mg/week!) they have problems (with ejaculation etc) because their natural testosterone production has decreased. In the same way, that a few months worth of T shots provides feedback to your brain and gonads (ovaries) telling them to stop female hormone production. Any natural male hormone production is also altered. Remember that you are overriding your body’s natural homeostasis (the body regulates itself such that everything is is equilibrium). After a shot, the body has stacks of T – so it doesn’t need to make any more. Remember though, you don’t have much natural T production to start with!

A bodybuilder who is abusing testosterone, will lose much of their ability to produce testosterone, simply because they are feeding their body so much of the stuff that their body says, “Oh hey! I’ve got loads and loads of testosterone, I’d better not make any more” and once they stop taking testosterone their body takes some time to realise it doesn’t have huge amounts of T floating around and that it needs to wake up the machinery that normally makes T, sometimes permanent damage is done.

In our case, like that of an androgen deficient natal-male, we are simply making up for a lack of natural testosterone. True, the small amounts of T that we did produce prior to seeking treatment are probably not being produced any more, but the injections more than make up for that.

If you have other questions about testosterone, please send them in and I’ll do my best to find answers for you and publish them on the website. Your GP should also be able to find answers for you.

Matt (2006) How T-Shots Work. Torque, 1(3), 7-9