General
Testosterone is the major male hormone, at the same time it is a powerful anabolic steroid. In malesit is responsible for development of male reproductive organs.
This hormone also promotes secondary sexual characteristics. It increasesmuscle mass, induce growth of body hair etc.Besides, it improves well-being and strengthens bones. Therefore, the lack of this hormone may cause bone loss and frailty.
It belongs to androstane family of steroids. Naturally it originates from cholesterol. Its final destination is liver, which transform it into inactive metabolites. Testosterone produces its effects through binding to androgen receptors.
The major source of testosterone in humans, as well as other vertebrates, is testes. Female ovaries also synthesize it, but much less. As a rulemales produce about 20 times more testosterone than females.
However, owing to higher metabolism, the concentration of testosterone in males is approximately 8 times higher than in females. This is also the reason of higher sensitivity of females to this hormone.
Testosterone is widely used for treatment of male testosterone deficiency (also ageing related) andcertain types of cancer in women. Meanwhile athletes use it to improve physique and performance.
Biologic effects
In the organism testosterone induces protein synthesis in tissues with androgen receptors. As a result, it causes growth of these tissues. This hormone has both androgenic and anabolic effect.
• Anabolic effect includesincrease of muscle mass and strength, linear growth and strengthening of bones and their maturation.
• Androgenic effect includes development and maturation of reproductive organs (penis, scrotum), as well as secondary sexual characteristics – voicedeepening, growth of facial and underarm hair.
Athletics
As we mentioned above athletes use Testosterone to increase muscle growth, strength and stamina. This happens owing to high protein synthesis in muscle cells. Thus, this hormone increases the size of muscles and speed up repair processes.
Testosterone Containing Products
Testosterone Cypionate
Easilyaromatizable; like other testosterones, it makes water retention a problem for many users. It is moderately toxic to the liver
Testosterone Enanthate
A bit heavier molecule with less prolonged activity than in Cypionate
Testosterone Propionate
Much faster acting than Cypionate and Enanthate. Also with less pronouncedandrogenic effects.
TestoJect, Aquatest
The most powerful testosterone. It is a pure testosterone without ester attached.
Testosterone Undecanoate (Nebido)
A uniquemedical product with extremely long action. It is widely used for testosterone replacement therapy.
Sustanon
Sustanon 250 – oil-based injectable mixture of 4testosteroneesters.
Sustanon 100 – similar blend, though with 3esters. Small doses of this drug are for paediatric use.
Testogel
is used as a cure for Testosterone deficiency in men.
Standalone usage is just fine for testosterone-replacement therapy.
Side effects
Androgenic side effects include oily skin, acne, alopecia etc. You can prevent them by using 5α-reductase inhibitors. In women it may cause virilization: voice deepening, excessive growth of body hair, clitoris enlargement etc.
Exogenous testosterone can suppress spermatogenesis in men, which may lead to reversible infertility. Since testosterone is prone to aromatization, at high doses it may cause gynecomastia.
However, you can prevent it by using aromataze inhibitors (read more about aromatization). Other side effects include mood changes, increased aggression and sex drive, spontaneous erections etc.
Interaction
5α-Reductase inhibitors
Such drugs asPropecia (Finasteride) can increase theamount of testosterone by suppressing its metabolism. On the one hand such medications reduce androgenic side effects, for example alopecia, acne, prostate hypertrophy.
On the other hand they reduce the natural levels of dihydrotestosterone (DHT), which is also important androgen for development of certaintissues. For example, they may delay puberty.
Besides 5α-reductase inhibitors suppress transformation of testosterone into 3α-androstanediol(important neurosteroid), which may lead to definite neuropsychiatric issues.
Aromatase inhibitors
Aromatase inhibitors (e.g. Anastrozole) suppress aromatase activity, thus preventing transformation of testosterone into estradiol. Since there is low level of testosterone transformation in the body, this does not influence the levels of this hormone.
However, it greatly reduce the risks of estrogen related side effects, such as gynecomastia. As estradiol negatively affects the hypothalamic–pituitary–testes axis (HPTA), the inhibition of its production may have positive feedback and increase the amount of endogenous testosterone.
Therefore, men suffering from secondary hypogonadism undergo Testosterone therapy along with aromatase inhibitors.
Conclusions
Due to its powerful effect on muscle growth, Testosterone is one of the most popular steroids amongathletes. Although it has some side effects, they can be prevented by definite medications (aromatase inhibitors, 5α-Reductase inhibitors).