Testosterone Side Effects

While testosterone may at times cause side effects, it is considered as one of the safest anabolic steroids to use due to the fact that the body naturally produces testosterone and therefore cannot be a cause for concern when talking about allergic reactions and the risk of anaphylactic shock. In fact, testosterone is the most widely researched anabolic steroid and has been the focus of many scientific and medical studies. There are plenty of solid, scientifically backed studies that prove testosterones safety and effectiveness, especially when compared to other modified analogs of testosterone.

While it is commonly known that modified analogs may avoid some of the side effects of naturally occurring testosterone, they themselves can present with some rather curious side effects of their own unknown to both science and medicine. This is due to the fact that, in effect, a completely new steroid has been created via modification and may exhibit side effects and symptoms that testosterone itself does not play host to. This is especially true because, as stated earlier, testosterone in its natural, unmodified state is found throughout the human body and is naturally tolerated.

It is therefore understood that the side effects of modified analogs and derivatives should not be experienced with testosterone itself, although that is not to say that testosterone does not come without its own set of possible side effects. However, the in-depth understanding of testosterone Propionate allows for side effects to be easily and effectively dealt with.

Estrogenic Side Effects

Testosterone possesses a small percentage of estrogenic activity. Estrogenic means that it can bind itself to the aromatase enzyme, which is the enzyme that converts testosterone to estrogen, and with estrogen being the female equivalent of testosterone. Therefore, estrogenic side effects are to be expected when using testosterone. In fact, those using testosterone in quantities as is seen in bodybuilding could expect to see a moderate rise in the levels of estrogen in the body. When high quantities of testosterone propionate are used for enhancing physique and endurance, a way must be found to deal with the significant increase in estrogen levels.

Some common side effects of increased estrogen are mood swings, swollen breast tissue and enlarged nipples (gynecomastia) fat deposits on more feminine areas such as the hips, thighs, and buttocks, softening and reduction of facial and body hair, and the possibility of water retention, bloating, and high blood pressure.

Gynecomastia from testosterone converting to estrogen

There are several options available for controlling the conversion of testosterone into estrogen. The first choice is to use aromatase inhibitor, which prevents the conversion happening by disabling the aromatase enzyme. An example of an AI and dosage would be 25mg per day of Aromasin (Exemestane) or Arimdex 1mg three time per week. Another option is to use a selective estrogen receptor modulator (SERM) such as Nolvadex, which blocks estrogen from binding to the receptors in breast tissue. However, a SERM such as Nolvadex will only counteract the effects of estrogen on the breast tissue and not of the amount of estrogen throughout the body. In effect, it would be best to combine the methods.

Androgenic Side Effects

Seeing that Testosterone is the most prolific male androgen, it is expected for Testosterone side effects will include androgenic effects too. During conversion, it is converted into DHT, which is a more potent androgenic metabolite. Dihydrotestosterone (DHT) is converted via the 5 alpha reductase enzyme which is found in larger quantities in the scalp, skin, and prostate.

The increase in DHT can lead to common side effects such as an increase in the rate of MPB (male pattern baldness) acceleration and increase in facial and body hair, Acne, excessively oily skin, and benign prostate hyperplasia (swelling of the prostate). The main concern of most men when it comes to DHT is its potential to attack the hair follicle and begin the process of follicular miniaturization en masse, or in other words, induce and speed up balding in men who are genetically predisposed to it.

To counteract the potential side effects that DHT may have on the body, there are several medications that can help. The first one is Proscar, which is a 5AR inhibitor and blocks the production of DHT, Dutasteride is another medicine which works in the same way. While both of these medications can help prevent or reduce the production of DHT, they won’t completely eliminate the androgenic effects completely as testosterone contains its own androgenic effects which can be found in tissues throughout the body.

Another method for combating DHT without using a 5AR inhibitor is by using Nizoral 2% shampoo which contains Ketoconazole, which effectively blocks the production of DHT in the scalp via a topical application. Therefore, Ketoconazole can help reduce the likelihood of male pattern baldness and reduce the amount of oil produced by the skin.

Testosterone Production Side Effects

Every single type of anabolic steroid can cause one of the most well known and documented side effects of endogenous testosterone production shutdown. Much like those who supplement with the hormone Levothyroxine for cutting fat, when the body already produces sufficient thyroid hormone the added addition of Levothyroxine can alter the thyroid glands production of thyroxine. This is especially true if you have more thyroxine in your system than normal. Over time the thyroid gland turns off its production of thyroxine and the user may have to supplement with Levothyroxine for life just to keep normal hormone levels. Testosterone Propionate is no exception and the shutting down of testosterone production is a real risk, especially for those who do not cycle their courses correctly or use testosterone Propionate for extended periods of time.

The possibility of the permanent shut down of the endocrine system can be mitigated by following proper post cycle therapy. Post cycle therapy or PCT is a vital part of a Testosterone based steroid cycle and consists of the user utilizing testosterone-stimulating compounds such as Nolvadex to assist in the normalization of the production of endogenous Testosterone. A proper PCT program should be followed for at least 6 weeks post cycle to ensure that all anabolic steroids have left the system and that the body is producing its own testosterone as normal.

Failure to follow a PCT program can result in the body failing to produce endogenous testosterone and lead to hypogonadism. Hypogonadism is the medical condition that results from the body not producing testosterone, and TRT (testosterone replacement therapy) will have to be followed for life to ensure that the body has sufficient testosterone for normal functioning.

Hepatotoxic Side Effects

Hepatoxic refers to the damage caused to the liver and liver cells, usually from medication, drugs, and supplementation. As Testosterone is not a C17 alkylated anabolic steroid, no hepatoxic side effects have been measured from its use. There have been many in-depth clinical studies performed to check the potential liver damaging effects that it may have, and to date, it has been proven to be safe.

Over a period of twenty days, several male test subjects were given 400mg of Testosterone Propionate each day orally. The choice to give the Testosterone orally rather than intramuscular was so that the liver became saturated with the testosterone supplement and the effects could be checked. (substances that are ingested orally make what is known as a ‘first pass’ through the liver. Intramuscular injections provide much less liver saturation. Therefore, oral supplementation would garner better results as more testosterone would pass through the liver)

The study concluded that no changes were observed from the use of testosterone Propionate on the liver (1). It is also important to note that Testosterone Propionate is normally administered via intramuscular injection, therefore, it does not undertake the ‘first pass’ through the liver, so even if any hepatoxicity had occurred, the normal route of administration would have little to no effect. It can then be said that Testosterone Propionate has zero concern regarding side effects and hepatoxicity.

Cardiovascular Side Effects

Testosterone related anabolic steroids can cause several peripheral side effects pertaining to the cardiovascular system, including negative cholesterol changes and strain. It is something that every single anabolic steroid in existence will cause and is part of the very nature of anabolic steroids, especially those administered orally. The effects on cholesterol are noted as a reduction of HDL and an increase of LDL, put in simpler terms, the good cholesterol reduces and the bad cholesterol increases. The impact on cholesterol levels greatly depends on several impacting factors ranging from the duration of Testosterone Propionate use, the quantity administered, and whether it is taken orally or intramuscularly.

Testosterone itself usually has less impact on the liver than other anabolic steroids due to the liver’s ability to freely use and breakdown testosterone, and testosterones low resistance to being broken down and metabolized by the liver. This is where the cause for concern shifts more toward other types of anabolic steroids, especially those that possess stronger resistance to metabolic breakdown than testosterone. Orally administered anabolic steroids pose much more of a risk of hepatoxicity than intramuscular and will show much more varied levels of hepatoxicity. This is important to know as for how quickly and easily an anabolic steroid is metabolized by the liver will directly influence the impact a steroid has on the liver’s ability to manage cholesterol levels.

In one clinical test, testosterone was shown to only mildly impact the HDL cholesterol levels over a 12 week period and with 280mg of testosterone Enthanate being administered weekly. When an aromatase inhibitor was added to the regime, things took a turn for the worse with a 25% drop in the amount of HDL cholesterol (2). However, in another study, which lasted 20 weeks and involved the subjects being given 300mg of testosterone Enanthate along with an aromatase inhibitor, a reduction of only 13% was observed. When testosterone levels were adjusted yet again to 600mg, a reduction of 21% was noted (3).

Cardiovascular damage from anabolic steroids

Another important effect noted was that the production of estrogen via aromatization and metabolization via the liver found that the estrogen helps offset the damage caused by the use of supraphysiological quantities of anabolic steroids. Of course, this makes perfect sense seeing the estrogen is known to possess positive effects over cholesterol. Anyone considering using anabolic steroids needs to take their cholesterol levels and the inhibitor they will use into account to minimize the risk of side effects pertaining to cholesterol.

Therefore, it is advised that to make use of minimal dosages of aromatase inhibitors to reduce estrogen levels rather than to completely eradicate it from the body. Ideally, the aim is to prevent estrogen levels from rising too quickly and too high and to also prevent them from being eliminated and spiraling towards zero. Without estrogen, the negative impact that could happen to the cholesterol levels would rise considerably. Too much estrogen in the system could lead to more feminization of the body as discussed earlier in the article.

Finding a suitable and safe middle ground when using anabolic steroids and aromatase inhibitors is imperative in maintaining a healthy and properly functioning body and hormonal balance. A small amount of estrogen is desirable as it not only helps prevent too much damage to the HDL cholesterol levels but also help ease the side effects caused by an excessive influx of testosterone. As with any medication or supplement, ensure that you perform some in-depth research as to what side effects you should expect and elicit advice from your physician or medical practitioner if possible. To understand the potential side effects and negative impacts along with the beneficial side effects and positive impacts will allow you to make a well-informed choice.

If you experience any serious side effects then discontinue your cycle and seek medical advice. While anabolic steroids do, of course, have the potential to cause detrimental side effects, if you follow the guidelines and instructions carefully and take note of the way your body responds, you can expect to enjoy the positives that they can provide too.


[1] Enzyme induction by oral testosterone. Johnsen SG, Kampmann JP, Bennet EP, Jorgensen F. 1976 Clin Pharmacol Ther 20:233-237

[2] High-density lipoprotein cholesterol is not decreased if an aromatizable androgen is administered. Friedl K, Hannan C et al. Metabolism 39(1) 1990;

[3] Testosterone dose-response relationships in healthy young men. Bhasin S, Woodhouse L. et al. Am J Physiol Endocrinol Metab 281:E1172-81, 2001