Testosterone

Development of the embryo

The testosterone is a male hormone which intervenes at the embryonic level to obtain a male Phénotype male embryos. It is secreted by the Cellules of Leydig and has a permanent and essential action on the seminal Vésicules and the Prostate.

The disappearance of the Canaux of Müller is caused by the secretion of AMH (Hormone Anti-Müllerienne), the testosterone as for it will support the differentiation of the Canaux of male Wolf of structure, i.e. in épididyme. In the differentiated channel seminal Vésicules and the Prostate are formed.

Between 9th and the 10th week, there are a big raise of the production and testosterone secretion by the Testicule. These peaks of secretion correspond well to the changes observed. These are the hormones testiculaires which are responsible for male differentiation.

At the time of the embryonic phase, the testosterone, with the Hormone antimullérienne (AMH), takes part in the installation of the sexual characters:

Paramount: installation of the Primary Testicles
: genital ways and external genitals which are:

various channels: épididyme and Spermiducte
additional glands: seminal Blisters and Prostate
the Penis

At the time of puberty (boys)

With the birth, the genitals (the Gonades) are differentiated, but are not functional. Morphological transformations as well as the setting according to the sexual Glandes are carried out with puberty.

With puberty (more or less early according to the individuals, but overall between 13 and 16 years), the secondary sexual characters develop:

Increase in the size of the Testicle S and the Pénis
general Pilosité
Accroissement in the muscular mass
Interêt for the reproduction
the testosterone rate again strongly increases

Complex hypothalamo-hypophyseal

Description

The Hypothalamus and the Hypophyse are connected by the pituitary Tige. The pituitary gland is placed in the turcic Selle.

It was noticed that the Castration male rat involves an increase in the activity of the former pituitary gland which one can stop by the injection of Broyat of testicle containing of testosterone. A testosterone injection directly in the former pituitary gland is without effect. On the other hand, an injection in the hypothalamus causes a fall of the activity of the pituitary gland and a regression of the testicles if the experiment is made on a “whole” rat.

The testosterone produced by the testicle has an action on the hypothalamo-hypophyseal axis. This action is Inhibitrice since it slows down the activity of the hypothalamus.

The integrating rétrocontrôle

The testosteronemy is the quantity of testosterone in 1mL of blood. This value always lies between 2 and 9 ng/mL at a normal individual. The testosterone slows down the secreting activity of the hypothalamus and the pituitary gland. It is fixed on cellular receivers. As it is manufactured following the activation of its release by the hypophyseal hormones (LH), it even released following an activation by the GnRH, hypothalamic neurohormone, one can say that the testosterone modifies the operation of the bodies which it " commandent" from where the term of rétrocontrôle. As it slows down their operation, it is said that it is a negative Rétrocontrôle or inhibiter.

Sources of testosterone

Following the example other hormones steroids, the testosterone is a derivative of the Cholestérol. It is in the Testicule S that the greatest quantities of testosterone are produced, but it is also synthesized in more minor amounts by the cells thécales and the ovary S, the réticuleuse zone of the cortico-suprarenal , and the Placenta. At the woman, most of testosterone is synthesized by “peripheral conversion”, i.e. to the site even of action, in fabrics. (This peripheral conversion is the primary source of testosterone at the ménopausée woman.) If one considers the whole of the sources of testosterone at the woman, by entering peripheral conversion, one estimates that the production at the woman is approximately 60% of testosterone produced at the man.

In the testicles, the testosterone is produced by the cells of Leydig. Considering the double function of the male gonade, the testosterone influences directly the spermatogénèse.

Like the majority of the hormones, the testosterone is brought to target fabrics by the blood, in which it is related to a plasmatic protein of specific transport, it (SHBG). There exists a balance between the fraction of testosterone fixed on the SHBG and the free fraction, only activates.

A study emanating of a laboratory of psychology of the University of Michigan tends to show that the production of hormones such as testosterone and progesterone could be stimulated or inhibited by psychological factors. The experiment consisted in making view with men and women of “romantic” films such as On the road of Madison , on the one hand, and of films plus violent one, such as the Godfather, 2nd part . The production of hormones is immediately affected, in a way different according to the sex from the subjects, but also according to whether they are naturally of important producers of a hormone or not. A third film, documentary “a neutral” on Amazonia, appeared without significant effects on the hormonal production.

Effects of testosterone at the human ones

It intervenes in the virilisation (the voice becomes more serious, the growth of the hairs is stimulated). The testosterone plays a part in the sexual desire (libido), in an unquestionable way at the man, and more or less at the woman. Its role in the activity - even aggressiveness - is established.

The testosterone takes part in the loss of hair of the men with the age.

Testosterone and doping

The external testosterone contribution has a beneficial effect on the doped Sportif S because it is a Psychostimulant which increases the potential of motivation of the sportsman. It also makes it possible to increase the muscular mass and the force as well as the fatigue strength (increase in the intensity of the drive). The exogenic testosterone consumption with aiming of doping is dangerous for health. Interdict since 1984 the exogenic testosterone contribution is detectable by an analysis which measures the report/ratio testosterone épitestostérone (near to 1 per 90% of the individuals). From 1984 to 2004, reports/ratios T/E up to 6 were tolerated, in 2004 this limit is gone down to 4. In the event of positive control with testosterone, an analysis complementary to the isotopic report/ratio of the Carbone is carried out in order to determine if the testosterone is of origin Endogène (generated by the body of the sportsman in a natural way) or Exogène (synthetic testosterone used for doping).

Chemical structure

The épitestostérone is a épimère (isomer) natural of testosterone. As many testosterone is produced than épistestostérone. It has the same role exactly as testosterone.

See too

References

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