drtbear1967

Musclechemistry Board Certified Member
What Is Testosterone? What Does It Do? How Does It Work?The first step towards the beginnings of understanding anabolic steroids and how they operate is through the thorough understanding of Testosterone itself. Quite literally, all anabolic steroids are synthetic derivatives of Testosterone, or a modification of a derivative of Testosterone. This is to say that Testosterone’s chemical structure is modified in a variety of different ways, and these modifications are what produce a brand new anabolic steroid – but it is regarded as a Testosterone analogue (or derivative). In this case, Testosterone is what is known as the precursor hormone to the derivative. Other descriptive terms also refer to Testosterone as being the parent hormone, or progenitor hormone of the derivative or analogue hormone. Testosterone is endogenously manufactured by the human body in the Leydig cells of the testes. The term ‘endogenous’ refers to the origin of Testosterone from within the body (referring to production within the human body by the body’s own cells), while the term ‘exogenous’ refers to the origin of a substance from outside of the body (through ingestion, injection, etc.).

There exist two other endogenously manufactured hormones within humans that are utilized as progenitor hormones to create anabolic steroid derivatives. These are: Nandrolone and Dihydrotestosterone (DHT).Testosterone is metabolized into Dihydrotestosterone in the body by way of the 5-alpha reductase (5AR) enzyme (this means that Dihydrotestosterone is a metabolite of Testosterone), and furthermore, Nandrolone is a byproduct of the aromatization (conversion) of Testosterone into Estrogen[1]. With this knowledge, it then stands to reason that Testosterone quite literally is the origin of all anabolic steroids. Without Testosterone, DHT and Nandrolone would not even exist, and therefore without the existence of DHT and Nandrolone, their individual derivatives and analogues would also not exist.Testosterone itself is the principal male sex hormone. Hormones are defined and classified as chemical messengers of the human body, which means that hormones are what send messages to different cells and tissues in the body to tell those cells and tissues what to do (grow muscle tissue, heal and repair, manufacture important components, perform a specific job, etc.). Without hormones of all different types, all functions within the human body will proceed unregulated and out of control.

How much Testosterone the average male produces is dependent on many different factors, which include: individual genetics, age, lifestyle habits, nutritional habits, and activity levels. On average, it has been determined that the median level of Testosterone production among males is between 50 – 70mg weekly. Where any given individual might land within that range is dependent on the aforementioned factors. It is common knowledge that the most prominent effects of the hormone Testosterone appear and are experienced during puberty, which is evidenced by an increase in Testosterone production and secretion, and will typically reach the highest endogenous levels at this point in any given man’s life. This significant increase in Testosterone serves to impart very important physiological changes of the male human body.

Testosterone governs many different functions within the body, as is typical of nearly all hormones. The nature of hormones is to govern systemic functions all throughout the body, and Testosterone is no exception to this.The Importance of Testosterone In the Body and its FunctionsAs the principal male sex hormone, Testosterone is responsible for governing the development and maintenance of male secondary sex characteristics (deepening of the voice, bodily and facial hair growth, increased sebum secretion on the skin, and development and growth of the male sexual organs which includes spermatogenesis (development of sperm) and increase in libido and sexual function. All of these functions are known as male secondary sex characteristics as well as androgenic (masculinizing) effects and they cannot function or develop properly or efficiently in an environment in which Testosterone levels are inadequate.

Although it is considered an androgenic effect as well, the muscle growth promoting effects have been categorized more independently as an anabolic effect. The word ‘anabolic’ refers to the promotion of tissue growth within the body, and in this case refers to the growth promotion of muscle tissue. This occurs through Testosterone’s ability to signal an increase in the rate of protein synthesis (the rate at which the body can synthesize and create new strands of contractile protein within muscle tissue). Hence this is why males on average naturally are more muscular than females and why males normally carry a heavier lean body weight than females do. Females possess very miniscule amounts of Testosterone, and this can be seen where it has been discovered that the average male endogenously produces approximately 2.5 – 11mg daily of Testosterone[2]. In comparison, females manufacture approximately 0.25mg daily of Testosterone, which is approximately 90% less (or 1/10th) than men. In females, their primary sex hormone is Estrogen, and it too is a steroid hormone, although not an anabolic steroid. By virtue of this distinction, Estrogen exhibits very different effects in the body compared to Testosterone, hence the vast differences between males and females. For example, women naturally possess a ‘softer’ tone and naturally hole more body fat than males do, which is a typical characteristic of Estrogen as it does promote fat retention/storage in various key areas of the body, which is important for female-specific roles (such as pregnancy and fetal development). In addition to this difference, females also exhibit a shorter height, vastly less muscle mass than men, and are far more prone to age-related bone deterioration. This is a direct result of the difference in hormonal dynamics between men and women.How Testosterone Specifically Works at the Cellular LevelAs with all hormones, the systemic and cellular effects of Testosterone are quite intricate, and involve various mechanisms that are both direct as well as indirect in its effects. All anabolic steroids share this property, as essentially, all anabolic steroids are derivatives of Testosterone and therefore possess much of the same properties just as a son shares the same genetic properties passed down from the parent.

There are many tissues in which Testosterone exhibits its effects. Of course, the beginnings of the journey in Testosterone’s job involve its transport systemically in the bloodstream as it is pumped throughout the body. Through this avenue of travel and transport, the hormone is free to travel to a variety of target tissues within the body and act as a messenger to tell those cells within those tissues what to do. The specific target tissues of Testosterone include muscle tissue (skeletal muscle), sub-dermal and dermal tissue (beneath the skin and the skin respectively), the scalp, kidneys, bone, the central nervous system, and prostate. What occurs in these tissues is the same general action and activity of all hormones: the hormone binds to a receptor situated either on or within the cell of the particular tissue type, and will initiate a message to the cell to instruct the cell to perform a particular job. In the case of steroid hormones, such as Testosterone and Estrogen, the specific receptors are located inside the cell. Testosterone will specifically bind to androgen receptors there in order to initiate its effects. Only steroid hormones possess the ability to bind to receptors located within cells, as the steroidal nature of Testosterone, Estrogen, Cortisol, or any other type of steroid hormone allows the hormone to be of a fat-soluble nature.

This is to say that the hormone will be able to easily pass through Chemical Messengers the phospholipid (fat) bilayer of the cellular membrane with ease. Peptide (protein) hormones cannot do this.Other hormone types such as peptide hormones (also known as protein hormones) must bind to receptors located on the outer surface of the cell membrane, as they cannot proceed inside the cell to interact with receptors there. Testosterone can therefore only affect tissues and cells in the body that retain the specific hormone receptor required (the androgen receptor), and therefore will only affect certain tissues and cells in the body. All hormones of all 3 types (steroid hormones, peptide hormones, monoamine hormones) operate in this hormone-receptor interaction, and this is what they all do. Although it is a very vague and non-specific description, the interaction with a hormone binding to a receptor site is described within science and biology as being very much like a lock and key, in which the key is the hormone and the lock is the receptor – both need to fit almost perfectly with one another for a specific action to occur.testosterone2Non-steroid hormones, such as peptide and monoamine hormones operate in the same lock and key manner, but they (as previously mentioned) will bind to and activate receptors located on the outer surface of the cell. The manner by which non-steroid hormones transmit signals through receptors is different from steroid hormones, whereby a peptide or monoamine hormone will bind to the receptor located on the surface of the cell, and this will enable various enzymes and proteins within the cell to act as messengers. These proteins that are then activated as messengers are known as ATP (Adenosine Triphosphate) and cAMP (cyclic AMP), which then travel within the cell to the nucleus of the cell in order to activate gene transcription. Although the general function of non-steroid hormones are the same as steroid hormones, the actual steps and specific action in certain stages is indeed different.As previously mentioned, Testosterone will enter the target cell(s) by diffusion through the cellular phospholipid bilayer (the layer that encases and encompasses the whole cell), and it will travel through the cytosol (the fluid-filled space inside of the cell) towards the androgen receptor. Once the receptor is located, Testosterone will then bind with the receptor to form what is properly known as the receptor complex. The complex (or ‘receptor complex’) refers to the now bound receptor and hormone together as one. When this occurs, the complex then travels to the nucleus of the cell, which is where it will activate certain DNA sequences.

These specific DNA strands/sequences are specific to the intention of Testosterone’s effects on the cell, and they are known as the ‘hormone response element’. For example, in the case of muscle cells, this will activate gene transcription (copying and reading of that specific code of DNA) that will instruct the cell to begin the synthesis and construction of contractile proteins that will ultimately increase muscle strength and muscle size. In layman’s terms, Testosterone is responsible for going into a cell, unlocking the container inside the cell that contains the instructions/blueprints for the cell to do a specific job, and it then tells the cell to do this specific job. In the example given with muscle cells, it informs the muscle cell to begin growth of new muscle tissue. Androgen receptor interaction within other cell types will initiate a different cellular response to the “reading” of these genetic sequences.

Within muscle cells, Testosterone does not only instruct the cell to begin the construction of new muscle cell components (which are the contractile proteins actin and myosin), but also expresses gene transcription of other functions, such as instructing the muscle cell to increase its storage capacity for carbohydrates in the form of glycogen (the useable form of carbohydrates for muscle energy). Following this signaling process, Testosterone will then dissociate (separate) from the receptor, breaking the receptor complex, where it is then free to either linger within the cell before re-engaging in receptor binding, or it may also leave the cell and return to circulation within the bloodstream. It is very important for the reader to understand, however, that this entire process in all of its stages is a slow process and occurs over the course of hours. Studies have demonstrated this time and time again where it has been found that on average, an anabolic steroid hormone requires approximately 4 – 6 hours before the hormone dissociates from the receptor within the cell[3]. These same studies have also demonstrated that new androgen receptors are created after the hormone has broken away from the receptor, which is a very strong indication that androgen receptor sites in fact increase in the presence of androgens, and that the prior theory of many years past that androgen receptors “saturate” as the prime reason for a reduction in progress on an anabolic steroid cycle is quite plainly untrue.Examples of other areas of the body in which Testosterone and related androgens will exert effects (but in a different end result) is in the kidneys, where Testosterone will, through the same signaling via receptor interaction, signal the cells of the kidneys to begin or increase the manufacture of a hormone known as Erythropoietin (EPO), which is a protein hormone that then travels to bone marrow and signals an increase in red blood cell production[4]. This is what leads to elevated red blood cell and higher hemoglobin levels while on an anabolic steroid cycle. “Hemoglobin levels” and “red blood cell count” are synonymous with one another, as hemoglobin is the protein contained in the center of each red blood cell, which is where oxygen becomes attached to when red blood cells travel to the lungs to pick up oxygen. The red blood cell then travels to various tissues and cells throughout the body to deliver the attached oxygen before returning to the lungs to allow more oxygen to attach to the hemoglobin protein. Therefore, a rise in hemoglobin levels will always correlate with a rise in red blood cell count.

The fact is that all anabolic steroids exhibit this effect of erythropoiesis, and although some anabolic steroids will stimulate erythropoiesis to a greater degree than others, they all exhibit this characteristic that is the result of the anabolic steroid’s interaction with androgen receptors in the cells of the kidneys. There is some evidence, however, to suggest that DHT (Dihydrotestosterone) and a few of its derivatives might not exhibit this activity in kidney cells because DHT is very quickly metabolized into non-active hormones by way of the 3-alpha hydroxysteroid dehydrogenase series of enzymes, which are present in very high amounts in the kidneys as well as muscle tissue[5].This 3-hydroxysteroid dehydrogenase enzyme, which is present in large quantities in muscle tissue (as well as certain other select tissues of the body such as the kidneys) serves to metabolize any DHT that enters muscle tissue into two inactive metabolites: 3-Alpha Androstanediol and 3-Beta Androstanediol. These two hormones, which are metabolites of DHT, are not anabolic at all in muscle tissue. This is therefore the reason as to why DHT is not anabolic in muscle tissue at any amounts, and many chemists and biologists believe that if this enzyme 3-hydroxysteroid dehydrogenase did not exist in muscle tissue, that DHT would actually be a very potent and powerful anabolic steroid. The key benefit in this situation that most DHT derivatives possess is that they contain chemical modifications that allow the hormone to now bypass this limitation whereby the hormone now does not interact with the 3-hydroxysteroid dehydrogenase enzyme and does not become metabolized by it. This allows the DHT analogue to enter muscle tissue (or kidney tissue) and exert its powerful anabolic effects on these cells.

Fat cells are also responsive to androgens such as Testosterone, and although through this they do not impose any dramatic fat loss, they still initiate lipolysis (fat breakdown) in fat cells[6]. It has also been found through this that the interaction of androgens with the androgen receptors in fat cells, the amount of beta-adrenergic receptors is also increased[7]. It is quite evident that Testosterone and related anabolic steroids do play a role in the regulation of body fat levels as evidenced by the fact that when the levels of Testosterone and androgens in general reduce for any reasons, body fat levels will increase[8]. This is very evident in females whom as mentioned earlier possess far lower levels of androgens than do males, but Estrogen also plays an increased role in body fat storage here as well, where Estrogen will increase the promotion and/or retention of body fat in specific areas of the body[9] as well as hypogonadism and andropause patients that will tend to gain increased body fat storage during their years of reduced Testosterone levels. This is one of the reasons that anabolic steroid using athletes and bodybuilders will, through different methods, elect to reduce or control Estrogen levels while on an anabolic steroid cycle.

The opposite occurs when androgen levels are increased, where the disposition of body fat to lean mass will become reduced in favor of a body composition that exhibits increased lean mass and decreased fat mass.Other cells and tissues of the body where Testosterone exerts its effects on androgen receptors includes the sebaceous glands in the skin, hair follicles in the skin, the scalp, the prostate, and certain other areas. The areas such as scalp, skin, and prostate are known as androgen responsive tissues. This is to say that these tissues are responsive specifically to androgens than other tissues, and to greater degrees. Testosterone’s interaction with the cells in these tissues is what brings about the secondary male sex characteristics experienced during puberty. This includes an increase in bodily and facial hair, as well as increased oil secretion of the skin where the sebaceous glands are concerned[10], and thus why acne can become a problem during puberty and during an anabolic steroid cycle in individuals who are sensitive to androgen activity in these tissues. These androgen responsive tissues in particular are designed to be more responsive to the stronger androgen Dihydrotestosterone (DHT), which is what Testosterone is reduced (or converted) into in these tissues. The scalp, skin, and prostate contain high levels of the enzyme 5-alpha reductase (5AR) are present, which is the enzyme that is responsible for the conversion of Testosterone into DHT. DHT binds far more strongly to androgen receptors than Testosterone does, and is therefore a stronger androgen, which is the overall intention in these tissues.In terms of the scalp and hair loss, which is a common concern among men, it must be understood that the individual must possess the genetic trait for male pattern baldness (MPB) in order to lose hair from increased androgen levels.

As mentioned previously, Testosterone and its stronger metabolite DHT can bind to androgen receptors located in the scalp, and through this, trigger male pattern baldness in individuals that possess the genetic trait required for the condition to manifest itself, and can occur in both men as well as women. Those who do not possess the specific gene required for activation will not experience this effect at any dose at all. This is why there are individuals that can utilize the most androgenic anabolic steroids, such as Trenbolone over and over again in cycle after cycle for years, and still end up with a full head of hair in their old age while others less fortunate will use very mildly androgenic compounds and experience hair loss. Testosterone does not, nor do any anabolic steroids cause hair loss – the individual’s hereditary genetics do, and Testosterone will serve to merely speed the process up that has already existed.
 
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