The function of testosterone
Testosterone, secreted first in the gonadal germ cells and then in the foetal testes, is responsible for the development of male physical characteristics, including the formation of the penis and scrotum, but not the scrotum. must be the clitoris and vagina.
In general, testosterone has a distinguishing effect that is characteristic of the male body. During foetal development, the testes are stimulated by chorionic gonadotropin to produce moderate amounts of testosterone throughout foetal development to approximately 10 weeks or more postpartum; then testosterone is almost not produced in childhood until about 10-13 years of age. Thereafter, testosterone production increases rapidly under stimulation of the anterior pituitary hormone gonadotropin with the onset of puberty and for most of the rest of life, after age 50, it declines rapidly and only 20-50% at the age of 80.
The function of testosterone in foetal development
During foetal development, testosterone begins to be secreted by the testes around week 7. In males, there is a gene on the sex chromosome Y (SRY) that encodes a protein called testicular determinant (also called a testicular determinant). SRY proteins). The SRY proteins initiate a gene activation sequence that causes the embryo's genital ridge cells to differentiate into cells that secrete testosterone and eventually become testes, while the female chromosome makes the protein. differentiate these cells into oestrogen-secreting cells. Injecting large amounts of male sex hormones into pregnant animals induces the development of male sex organs even though the foetus is female. In contrast, removal of the testicles in the early stages of male foetal formation causes the development of female genitalia. So, Testosterone, secreted first by the gonadal germ cells and then in the foetal testes, is responsible for the development of male physical characteristics, including the formation of the penis and scrotum, but not must be the clitoris and vagina. It also induces the formation of prostate, seminal vesicles, vas deferens and male genitalia while inhibiting the formation of female genitalia.
Figure: Different stages of male sexual function, as shown by serum testosterone levels (red blood sugar), and sperm production (blue line) at different age groups.
What is the function of testosterone in the cause of hypogonadism?
The testicles usually fall into the scrotum during the last 2-3 months of pregnancy when the right amount of testosterone is secreted. If a child is born with an undescended testicle but is abnormal, testosterone usually works to lower the testicle in the usual way if the inguinal canal is wide enough to allow the testicle to pass.
The hormone gonadotropin, which stimulates the Leydig cells of the newborn testicles to produce testosterone, may also determine testicular hypoplasia. Thus, the hypogonadism is caused by testosterone stimulation, again showing that testosterone is an important hormone for male reproductive development during foetal life.
Effects of testosterone on the development of primary and secondary sexual characteristics in adults
After puberty, increased testosterone secretion causes the penis, scrotum, and testes to increase in size about eight times before the age of 20. In addition, testosterone also causes secondary sexual characteristics in male development. gender, beginning in puberty and ending in adulthood. Secondary sexual characteristics, in addition to the sex organs, by which male and female are distinguished.
Affects hair growth
Testosterone affects hair growth (1) on the pubic bone, (2) along the midline of the abdomen sometimes to the navel and above the navel, (3) on the face, (4) more commonly on the chest, (5) the Other areas are less common, such as the back. That is also the reason hair is present on most parts of the body and makes the body fuller
Male pattern baldness
Testosterone reduces hair growth on the crown of the head, a man without testicles will not go bald. However, men with many penises also never go bald because baldness is the result of two factors: genetic factors and the number of androgen hormones. When an androgenic tumour grows long-term, a woman with a particular genetic background can go bald just like a man.
Testosterone secreted by the testes or injected into the body causes mucosal hypertrophy and the development of the larynx. That influence is initially disproportionate, the phenomenon of "voice cracking" gradually changes to a typical masculine voice.
Testosterone increases the thickness of the skin and can contribute to acne development. Testosterone increases skin thickness throughout the body and the firmness of subcutaneous tissues. Testosterone also increases the secretion of the body's sebaceous glands, especially the sebaceous glands of the face, which can cause acne. Therefore, acne is one of the common features in young men when the body begins to increase testosterone production. After a period when the liver secretes testosterone (maybe several years), the skin usually adapts to the changes caused by testosterone and the acne will disappear.
Testosterone increases protein and muscle growth
One of the most important features in the male body is muscle growth after puberty, about 50% more muscle mass than in girls. An increase in muscle mass is always associated with an increase in non-muscle protein. Many skin changes are caused by protein deposition in the skin, and voice changes are also a result of testosterone's anabolic protein function. Due to the tremendous effects that testosterone and other androgens have on the muscular system, synthetic androgens are widely used by athletes to improve their muscular systems. In fact, this is strongly opposed due to the harmful effects of androgen excess, in relation to sports physiology. Testosterone and synthetic androgens are also sometimes used in old age as a “youth hormone” to improve strength and vitality, but the results are questionable.
Testosterone in bone structure development and bone calcium content
After a dramatic increase in circulating testosterone during puberty (or after prolonged testosterone injections) bone thickens and thickens significantly with calcium salts. Thus, testosterone increases the number of bone structures and causes calcium deposition. Bone growth is thought to be the result of the general anabolic function of testosterone with the deposition of calcium salts in response to increased protein. Testosterone acts on the pelvis to (1) narrow the pelvis, (2) lengthen the pelvis, (3) tubular instead of the horizontal oval-like in women, (4) increase the strength and endurance of the body. Pelvic. In the case of testosterone deficiency, the male pelvis develops similarly to that of the female. Because of its ability to increase the size and number of bones, it is sometimes used to treat osteoporosis in older men. When large amounts of testosterone (or another androgen) are abnormally secreted in a growing child, the rate of bone growth increases markedly, causing a dramatic increase in body height. However, testosterone also causes the growth plates of bone to become fused with the bone body. Thus, despite the rapid growth rate, this alignment of the growth plates prevents the adult male's height increase and testosterone is not secreted at all. Even in ordinary men, the final height is not reached like the eunuch men Despite the rapid growth rate, this alignment of the growth plates prevents the adult male's height increase and testosterone is not secreted at all. Even in ordinary men, the final height is not reached like the eunuch men Despite the rapid growth rate, this association of the growth plates prevents the adult male's height increase and testosterone is not secreted at all. Even in ordinary men, the final height is not reached like those of eunuchs
Testosterone increases basal metabolism
Injecting large amounts of testosterone can increase basal metabolic rate by about 15%. In addition, even normal testosterone secretion during adolescence and early adulthood increase the metabolic rate by 5-10% compared with inactive testes. This metabolic rate may be an indirect result of testosterone's effect on protein assimilation, together with an increase in specific protein-enzymes-increasing the activities of all cells.
Testosterone in increasing red blood cell count
When the usual amount of testosterone is injected into a castrated person, the number of red blood cells per cubic millimetre of blood increases by 15-20%. Thus, the average man has about 700,000 more red blood cells per cubic millimetre than the average woman. Despite the close association between testosterone and increased haematocrit, testosterone does not directly increase erythropoietin levels or have a direct effect on red blood cell production. The effect of testosterone on increased red blood cell production may be indirectly contributed by the increased metabolic rate following testosterone injection.
Effects on water and electrolyte balance
Many steroid hormones can increase reabsorption in the distal renal tubule, and testosterone has the same effect, but only to a lesser extent than mineral corticosteroids in the adrenal glands. However, after puberty, the blood and extracellular volume of males in relation to body weight increase significantly, about 5-10%.