As 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. 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 Level:
As 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.
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, mono-amine 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.
Non-steroid hormones, such as peptide and mono-amine 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 mono-amine 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.
Although it is considered an androgenic effect as well, the muscle growth promoting effects have been categorized more independently as an anabolic effect.
How Testosterone Specifically Works at the Cellular Level:
As 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.
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, mono-amine 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.
Non-steroid hormones, such as peptide and mono-amine 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 mono-amine 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.
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