 The main hormone Testosterone has various functions and it acts in various phases of life either in its basic form that is Testosterone or after getting converted to Dihydrotestosterone by the enzyme Phivalpha reductase which is present in the cytoplasm of cell also it can even get converted to another hormone Estrogen so its functions may be by direct action of Testosterone or by Dihydrotestosterone or as Estrogen so let us see which of these forms causes which functions. First of all Testosterone is produced from genital ridge from seventh week of intrautrient life and then it is produced from Testis so remember Testosterone is not required for the development of Testis since it is being produced from it but it is required in fetal life for the differentiation of Wolfe and Dux into male reproductive tract so development of Testis does not depend on Testosterone but the male reproductive tract that is Epidermis, Vars, Difference, Ejaculatory Drugs, Seminal vesicles and Prostate Gland they all depend on the Testosterone not only that it is the development which is caused by Testosterone also in adult life further tract has to be maintained also so if Testosterone is not there then there will be degeneration in this parts of the male reproductive tract so it also causes the maintenance of these parts of male reproductive tract then just before birth it is required for the descent of Testis from abdomen to scrotum so these are the functions of Testosterone before birth that is the development of male reproductive tract and for the descent of Testis then after birth till puberty we see that Testosterone levels actually decline and it again comes into role at puberty and then throughout adulthood it is present so at puberty what are its function well first and foremost is spermatogenesis so the formation of the sperms depends on Testosterone then growth of external genitalia and development of secondary sexual characteristics so external genitalia that is penis and scrotum depend on the presence of Testosterone and development of secondary sexual characteristics so what are these secondary sexual characteristics well these include increase in protein formation and muscle development and by virtue of increased protein formation it also causes increase in bone matrix causing thickening of bone along with deposition of calcium salts then it is responsible for male pattern distribution of hair that is a hair over pubis which extends up to umbilicus and then appearance of beard over face appearance of hair over chest and male pattern baldness then it causes thickening of skin and increase in secretion from sebaceous glands which is responsible for appearance of acne at puberty plus there are many other changes which occur like the changes in voice which occurs and that is due to the hypertrophy of the laryngeal mucosa enlargement of larynx and vocal cords also increase in length and thickness so all this leads to deepening of voice then changes in torso the male body contour which develops changes in pelvis so it causes narrow pelvic outlet which is in contrast to that of females who have broad pelvis then it causes a strengthening of the pelvis for weight bearing plus there are also changes in mental attitude so it is responsible for aggressive behavior of females and increase in sex drive now among all the functions which we have just seen which are the functions caused by testosterone which are by dihedral testosterone and which by estrogen so let us try to categorize them see testosterone is responsible for development of internal genitalia during fetal life that is the male reproductive tract which we were talking about and also for their maintenance throughout adult life then in adults it is also directly responsible first permatogenesis and male libido plus for secondary sexual characteristic it is responsible for protein anabolic effect now dihedral testosterone dihedral testosterone we said that it is formed in the cytoplasm where five alpha reductase enzyme acts on testosterone and causes the formation of dihedral testosterone so this is responsible for development and enlargement of external genitals that is penis and scrotum and also for the development of prostate gland now you might be aware that there is something known as benign prostatic hyperplasia and in this condition if we give a drug of finasteride which is a five alpha reductase blocker so it blocks the enzyme five alpha reductase so what will happen dihedral testosterone will not be able to form from testosterone so obviously it will not be able to act on prostate gland so that is the reason that finasteride which is a five alpha reductase blockers works in benign prostatic hyperplasia fine so DHT is responsible for development and enlargement of external genitals then this enzyme five alpha reductase is also present in cells of skin and scalp so you can guess i think here that if it is present on scalp then male pattern bondness will be due to what it will be due to dihedral testosterone then growth of facial hair development of acne and hairline recession all are due to DHT because this enzyme is present in skin and scalp by the way you should remember one thing that formation of DHT is a way of amplifying the action of testosterone on the target tissues because what happens that this DHT and testosterone combined with the same receptor but the combination of DHT with that receptor is more stable than that of the testosterone receptor complex and that is why it is able to act better so this is a way of amplifying the action of testosterone in the tissues now you just remember this because in the end we are going to solve one question and it is very interesting to know this concept now finally testosterone as I said earlier can also act after getting converted to the hormone estrogen so estrogen is very important for spermatogenesis so it plays a role in spermatogenesis in epididymis actually it is present and it is responsible for fluid resorption from there so estrogen is important for spermatogenesis and estrogen is also responsible for attraction of males to opposite sex so it acts on brain cells and is responsible for heterosexuality and finally estrogen is also responsible for closure of the epiphysis so testosterone is converted into estrogen in bone also so testosterone is directly causing the bone growth but the closure of epiphysis occurs when testosterone gets converted to estrogen by the way it's the enzyme aromatase which acts on testosterone and converts testosterone to estrogen okay so these were the functions of testosterone which acts as directly as testosterone dihydrotestosterone or estrogen but before closing as I mentioned earlier let's try to answer one question what will be the problem in a child with congenital deficiency of five alpha reductase so here are some four options given whether the problem will be in spermatogenesis whether the problem will be in wolfian duct formation that is the formation of the male reproductive tract will it cause wolfian duct regression as the option says or it will cause male pseudo hermaphroditism or it will cause shorter stature well the answer here is C male pseudo hermaphroditism very interesting it is first of all what is pseudo hermaphroditism well it means that internal genitals are normal like that of male but external genitals are looking like that of female now we have said that testosterone directly is responsible for formation of internal genitals while for the development and enlargement of external genitals dihydrotestosterone is needed and this is formed when five alpha reductase enzyme acts on testosterone isn't it so in this case internal genitals will be that of male while external genitals will look like that of a female so that is why in this case the person is suffering from male pseudo hermaphroditism so what happens that such a male is actually raised as a female but at puberty some growth of genital occurs because at puberty there is high concentration of testosterone and even though the amplifying effect of dihydrotestosterone is not there but yet testosterone by virtue of increased concentration starts having some effect on the external genitals right and this causes the development of the genitals and the body contour also changes and the libido develops so these children are raised as females but later on convert to males fine so that's the answer to this question but quickly you might have understood that why the other things will not occur well first option spermatogenesis we said testosterone is directly responsible for spermatogenesis then a wolfian duct regression will not occur because it is the testosterone in its form only that causes the development of male internal genitals and a shorter stature again will not be there because the protein anabolic effect which causes increase in growth is again directly by the hormone testosterone so that's all for the functions of testosterone if you like the video do press the like button and do share the video with others and don't forget to subscribe to the channel Physiology Open thank you