Metabolic changes, which lead to synthesis of proteins, fats and saccharides, are called anabolic. Their counterweights are the mechanisms, which are called catabolic. They are responsible for decomposition of complex structures like proteins or fats. By a healthy person, the anabolic and catabolic processes are always balanced – this state is called metabolic balance. Anabolic steroids are substances, which are very similar to the male hormone testosterone and for this reason; they can have influence on the growth of muscles.

Testosterone from laboratory

Synthetic anabolic steroids were developed by a suitable modification of the molecule of testosterone. By this modification, several types were developed, which have slightly different characteristics. For this reason, various steroid products have different quality of androgen (contributing to male characteristics) and anabolic (contributing to the growth of muscles) effects. The aim to suppress the androgen action of testosterone led to the development and production of so called anabolic steroids, which actually never caused the suppression of anabolic properties. For example, some anabolic steroids, as for example Anavar, contribute to the development of male characteristics only minimally, and are for this reason often used by women. Unfortunately, such steroids do not contribute to the growth of muscles very much. This led to the opinion, that these two effects cannot be divided.

Difference between oral and injectable testosterone

The modification of testosterone helped to develop anabolic steroids, which are absorbed slowly in the body. If you take orally natural testosterone, it will be immediately absorbed by the liver. If you apply it orally, it goes at first to the liver and after it to muscles. Up to 98 % of testosterone is absorbed already during its first pass through the liver. Testosterone, which was taken per injection, goes at first into the muscles and after it to the liver. However, 98 % of testosterone is absorbed during its first pass through the liver, as well.

To be effective, anabolic steroids have to be able to pass several times through the blood flow, before they become ineffective. The modification of the molecule of testosterone and a use of a group of alkyls on a specific place (known as Alfa position, AKA place on the 17th carbon) led to the development of anabolic steroids, which can be hardly absorbed by the liver (Alfa-alkylated). Anabolic steroids based on this principle are able to pass several times through the liver and they become ineffective much later. It means that anabolic steroids are able to get in the muscles, act there and have the desired effects. However, the liver is forced to work much harder. A majority of oral steroids was developed by this or very similar way and thus they can lead to dysfunctions of liver.

Injectable steroids are not based on this principle, so they are generally less dangerous and mostly they are not as harmful for the liver. However, some anabolic steroids, stanozolol, for example (produces in both oral and injectable form), are chemically very similar to the oral ones and have the same effects (including the negative ones).

Esters of testosterone

Esters of testosterone have the main role in the injectable steroids. Ester is a substance, which is produced by a reaction of a fatty acid and alcohol (in case of anabolic steroids, the esterification of a steroid molecule on the place of 17th carbon is made). Esterification made testosterone effective although it passes only once through the blood flow, before it is absorbed by the liver. The majority of injectable steroids is applied intramuscularly, for this reason, the active substance gets at first to muscles and after that to the liver. These esters act for a longer time and are less dangerous than the oral Alfa-alkylated steroids.

The more carbons are present in the fatty acid, the slower is the release of the steroid ester from the place of application to the blood flow and the longer is the biological effectiveness of the injectable product. For this reason, it is possible to apply injections in longer intervals. Amongst the most widely used acids for the esterification are: propionate (3 carbons), enanthate (7 carbons), cypionate (8 carbons), phenylpropionate (9 carbons), decanoate (10 carbons), undecanoate (11 carbons), laurate (12 carbons), hexylophenylpropionate (15 carbons).

Just a few esters (methenolone acetate and testosterone undecanoate, for example) can be taken orally. It is not completely clear, why methenolone acetate is effective in the oral form, as well. Testosterone undecanoate goes to the blood flow through the lymphatic system, thus it bypasses the liver from a majority. These two esters are less toxic for the liver than other oral steroids.

The anabolism of proteins leads to the reduction of elimination of urea (waste product of the metabolism of proteins) without simultaneous changes in elimination of uric acid, ammonia and nitrogen. What is more, the elimination of phosphate, chloride, calcium, sodium and potassium is reduced. However, when the nitrogen balance gets back to normal, the anabolic effect does not continue. In this moment, the phase of decomposition begins.

When the intake of steroids is stopped, the negative nitrogen balance usually appears which is connected with a considerable loss of body weight. The lost weight depends on the type of the used medicaments, period of its use, dosage, their total amount and the physiological state of the individual.