A Guide to Steroid Metabolism


The term used to signify the complete set of reactions in the organisms producing or consuming steroids is called steroid metabolism.

Steroids include testosterone, estrogen, progesterone and cortisol. While testosterone is the male hormone and is naturally made in the male testes, progesterone and estrogen are made up in the placenta and the ovary- the female sex glands.

Testosterone is converted into progesterone and estrogen on the fly in both the males and females in order to regulate the balance of the respective hormones in the body.

There are certain enzymes and reactions in the nervous system that bring these changes about and artificial steroids increase the levels of hormones in the body- thereby bringing exaggerated effects. Steroid Metabolism is broadly divided into three phases namely synthesis, genesis and degradation.

Steroid Synthesis

This is the process of producing or manufacturing steroids using simpler substances or precursors. Technically speaking, this is an anabolic metabolic process and results in creation of a pathway for the synthesis and production of steroids.

There are different pathways created in different organisms and in the case of human beings, it is the Mevalonate Pathway where the synthesis starts out from.


This is the process in which steroids are produced from cholesterol. The term also encompasses the process in which the first level steroids manufactured from cholesterol are transformed into other types of steroids.

The main products of steroidogenesis include androgens (testosterone), corticoids (aldosterone, cortisol), estrogen and progesterone. It would be worth noting that this is almost an exhaustive list of steroids that might actually be of importance to human beings and therefore, this is one of the most important steps of steroid metabolism.

Elimination of Steroids

This is the final step of steroid metabolism and is one of the most important processes. The elimination of steroids is very important from the body in order to maintain hormonal balance.

Scientifically, the steroid rings are typically oxidized by cytochrome oxidase enzyme which weaken the steroid ring. The weakening of the steroid ring helps the other enzymes into breaking up the steroid structure to form bile acids as the end products. These bile acids are handled by the liver and are secreted out in the bile- thus ensuring that the body is clear of the end products.

How they act

There are three main ways of administering steroids into the body- oral tablets, skin patches, and by injection. Although oral administration of steroids is the easiest, the testosterone that is actually used up at the end of the dosage is just about 1/6th the administered levels. This is due to the fact that the steroids are rapidly absorbed when taken orally and are then
converted into useless metabolites.

These are not only useless, but sufficiently difficult for the liver to break down. Thus, the intake has to be low- which means that even lower volumes of testosterone are actually available to act on the body.

Skin patches are also available to provide doses of the hormone to the bloodstream at a steady pace. Because oral administration can lead to liver damage over a period of time intermuscular injections are the most preferred way of using steroids. When steroids are injected they bypass the liver which is easier on the body.

Steroids act by penetrating the membrane of the cells they are supposed to act on. After this penetration is through, the steroids cling themselves onto the anabolic receptors of the cells. These receptors are located in the cytoplasm (one of the main areas of the cell body) of the cell.

After this, the substance diffuses into the nucleus of the cell. The nucleus is the center of activity in the smallest part of an organism- the cell. After entering the nucleus, the steroids start acting on the cell and bring about hormonal changes that are responsible for bringing about the desired changes- weight gain and increase in the lean muscle mass.

Steroids are known to bring about the increase in muscle mass in two ways – first up, they increase the synthesis of protein in the body and secondly, they inhibit the tiring up of the muscles (a process otherwise termed as catabolism- the reverse of metabolism).

An increased protein synthesis helps the body in gaining weight and also supplies the body with additional energy and strength to workout without tiring. The inhibition of catabolism further inhibits the production cortisol- the stress hormone of the human body. This leads to the body being less fatigued during workout- which results in a more stringent workout combined with aggressive energy.

Some AAS have also known to increase the BMR (or the Basal metabolic rate) which greatly reduces the fat content of the bodythereby making more room for the muscles to expand. This explains as to why the use of steroids leads to a lean muscle mass increase.

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