Anabolic steroid drugs: basic concepts

In order to understand how anabolic steroid drugs affect our body, it is necessary to introduce several concepts. Don't be afraid - no special knowledge is required from you.

A substance is called endogenous if it is produced by the body (endogenous testosterone is testosterone produced by the body), and exogenous if it enters the body from outside. All existing routes of drug administration can be divided into two large groups: enteral (through the digestive tract) and parenteral (bypassing the digestive tract). The former include: administration through the mouth (orally), absorption under the tongue (sublingually), administration into the duodenum and into the rectum (rectally); the latter include administration of drugs by injection, usually into a muscle, under the skin or into a vein. As for the anabolic steroid drugs that interest us, they are administered either orally or by intramuscular injection; it rarely makes sense to administer them sublingually. Drugs such as insulin or growth hormone are administered by subcutaneous injections.

Drugs administered through the digestive tract must pass through the liver before entering the general bloodstream. The liver is always on guard, protecting our body from foreign substances, many of which can be poisonous. The liver will destroy, to the extent possible, any substance that it considers foreign. Thus, the amount of active substance that enters the general bloodstream is usually smaller than the amount that was introduced into the body. The ratio between the first and second numbers is called the bioavailability of the drug. Simply put, bioavailability shows what percentage of the administered amount of the drug will actually work.

Most drugs undergo biotransformation in the body, i.e. various transformations. There are two main types of drug transformation: metabolic transformation and conjugation. The first means the transformation of substances due to oxidation, the second is a biosynthetic process accompanied by the addition of a number of chemical groups or molecules of endogenous compounds to the drug or its metabolites. Anabolic steroids undergo both metabolic transformation and the subsequent conjugation in the body.

Almost all transformations that occur in the human body require some help "from the outside". If you haven't completely forgotten your school chemistry course, you'll easily remember that substances that speed up chemical reactions are called catalysts. Catalysts of chemical reactions that occur in any living organism are called enzymes. But in addition to catalysts, there are also other substances that slow down chemical reactions. Their name is inhibitors.

The effect of drugs is largely determined by their dose: the higher it is, the faster the effect of the drug develops, depending on the dose, the severity, duration, and sometimes the nature of the effect changes. A dose is the amount of a drug for one dose - this is a single dose. Doses are divided into threshold, average therapeutic, highest therapeutic, toxic and lethal.

• The threshold dose is the dose at which a drug causes an initial biological effect.
• The average therapeutic dose is the dose at which the drugs produce the required pharmacotherapeutic effect in most patients.
• Higher therapeutic doses are used when the desired effect is not achieved with medium therapeutic doses; it is worth noting that in the case of higher therapeutic doses, the side effects from the use of the drug are still not expressed.
• In toxic doses, drugs begin to cause toxic effects that are dangerous to the body.
• Well, I think I don’t need to explain to you what lethal doses are.

The difference between the threshold and toxic doses of a drug is called the therapeutic range.

Repeated use of drugs often results in a decrease in their effectiveness. This phenomenon is called tolerance (habituation), and may be associated with a decrease in the absorption of the substance, an increase in the rate of its inactivation, or an increase in the intensity of excretion. Habituation to a number of substances may be due to a decrease in the sensitivity of receptor formations to them or a decrease in their density in tissues.

In order to judge the rate of elimination of substances from the body, a parameter such as half-life (or half-elimination, as you prefer) is used. Half-life is the time after which the concentration of the active substance in the blood plasma decreases exactly by half. It is also worth keeping in mind that the half-life is determined not only by the elimination of the substance from the body, but also by its biotransformation and deposition. Now about the receptors, they serve as one of the "targets" for drugs. Receptors are called active groups of substrate molecules with which the substance interacts. Receptors, like other molecules, have a certain half-life: a reduction in this period leads to a decrease in the number of corresponding receptors in the body, and an extension, naturally, to an increase in this number. Let's distract ourselves from all other receptors, in the future we will be interested only in hormonal receptors, and we will pay special attention to androgen receptors. All hormone receptors can be divided into two broad categories: receptors inside cells (these include receptors for steroid and thyroid hormones) and receptors on the cell surface (all others, including receptors for growth hormone, insulin-like growth factor, insulin, and adrenergic receptors). It should be noted that the number of receptors on the cell surface can decrease (this phenomenon is called downregulation), and sensitivity to the corresponding drug can thus decrease. Receptors inside cells are not subject to downregulation (at least, there is no documentary evidence of this).

Androgen receptors (AR) of course also fall under the general definition of receptors. To put it simply, androgen receptors are very large protein molecules consisting of about 1000 amino acids and located inside cells. Different cells, it must be said, not just muscle fibers. Previously, it was believed that there were several types of androgen receptors; now everyone knows that there is only one.

It should be noted that molecules of different substances can bind to the same receptor. The effect they cause also varies significantly. Substances whose molecules bind to receptors are divided into two large groups - agonists and antagonists. Agonists are those substances whose molecules, binding to receptors, cause a biological effect. If we talk about hormonal receptors, their agonists copy the action of endogenous hormones, more or less successfully. Endogenous hormones themselves, of course, are also agonists. Antagonists also bind to receptors, but do not produce any effect. Antagonists are a kind of "dog in the manger": without the ability to activate the receptor, they at the same time do not allow agonists to join the receptors and do something "useful". The use of antagonists at first glance seems pointless, but only at first glance. This group of substances includes, for example, some antiestrogenic drugs; By blocking estrogen receptors, they virtually eliminate the risk of side effects associated with AAS aromatization.

Well, these are probably all the basic concepts we need to understand how anabolic steroid drugs work.

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