maanantai 5. tammikuuta 2009
Testoartikkeli Muscle News -lehdessä
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Testosterone – Part I
Testosterone separates men from the boys. Testosterone increases the synthesis and decreases the breakdown of protein, leading to an increase in the rate of growth. In addition, testosterone plays a key role in health and well-being. In the first part of this article, we explain what testosterone is and how it affects the body.
Testosterone, the principal hormone of the testes, is a anabolic steroid synthesized from cholesterol in the Leydig cells and is also formed from androstenedione secreted by the adrenal cortex. The secretion of testosterone is under the control of luteinizining hormone (LH). The testosterone secretion rate is 4-9 milligrams per day in normal adult men. Around 98% of the testostosterone in blood is bound to proteins. In general, only non-bounded (free) testosterone has biological activity.
The key testosterone effects are as follows:
- Maintenance of muscle mass and strength
- Maintenance of bone density and strength
- Libido and penile erection frequency
- Mental and physical ”energy”
However, these effects decline as testosterone levels decline in the later decades of adult life. Unfortunately, anti-doping hyperbole over the years has been the major detractor from the treatment of clinical states that could be caused by or related to low testosterone levels.
Also, the unwarranted fear that testosterone therapy would induce prostate cancer has also deterred doctors form pursuing more aggressively the possibility of low testerone levels in patients. While it may exacerbate an existing prostate cancer, there is absolutely no evidence to implicate testosterone as a cause of prostate cancer. Androgen-deprivation therapy (i.e., reduction of male hormone levels) is generally employed in the treatment of locally advanced and metastatic prostate cancer. Although its use as an adjuvant therapy has resulted in improved survival in some patients, androgen-deprivation therapy has serious adverse effects. For example, Galvao and colleagues reported that after 36 weeks of androgen-deprivation therapy there was, as expected, a significant decrease in muscle and bone mass, while body fat increased.
At moderate doses, testosterone improves the mood, is a anti-depressant, and do not lead to aggressiveness.
While the focus of this article is the natular testosterone produced by the body, I will cite some studies using supplemental testosterone to high-light the benefical effects of higher testosterone levels.
Firstly, some medical authorities have grossly mislead the general public about the effects of testosterone and other anabolic steroids, i.,e, they downplayed how well anabolic steroids work and exaggerated the side-effects. Probably the most well-known anti-steroid fanatic was Dr. Allan Ryan. He adamantly stated that steroids did not work, any strength gains were purely psychological and any muscle size gains were purely from water retention.
In 1978, he published an pseudo-scientific article titled "Anabolic Steroids: The Myth Dies Hard" in The Physician and Sportsmedicine. Dr. Allan was not satisfied with the original 1977 Americal College of Sports Medicine position stand he had a major influence in forming, so he suggested changes to even further claims steroids do not work. Below is the original statement with Dr. Allan´s proposed changes as follows: Those words he wanted to omit are in italics with a line through it [ei näy alla] and those words he wanted to insert are underlined in [brackets] [ei näy alla].
"The administration of anabolic-androgenic steroids to healthy humans below the age of 50 in medically approved therapeutic [any] dose often does not [consistently] of itself bring about any significant improvement in strength, aerobic endurance, lean body mass, or body weight."
However, the efficacy of testosterone therapy in increasing muscle mass and strength was confirmed scientifically in 1996. Bhasin and co-workers randomly assigned 43 normal men to one of four groups: 1) placebo (i.e., inactive fake drug) with no exercise; 2) testosterone with no exercise; 3) placebo plus exercise; and 4) testosterone plus exercise. The subjects received injections of 600 milligrams of testosterone enanthate or placebo weekly for 10 weeks. The men in the exercise groups performed standardized weight-lifting exercises three times weekly. The results demostrated that testosterone, especially when combined with weight training, increases muscle size and strength without increasing the occurrence of angry behavior. The old theory that increased muscle and strenght gains are secondary to more intense and aggressive weight lifting in steroid users is clearly fallacious as it cannot account for muscle and strenght gains seen after testostosterone administration in the absence of weight training.
While its is well-established that testosterone increases the synthesis (anabolism) and decreases the breakdown (catabolism) of protein, the mechanisms behind these effects are still somewhat unclear. However, it is now evident that testosterone induces muscle growth by multiple mechanisms, including its effects on satellite cells. Satellite cells are able to fuse to augment existing muscle fibers and to form new fibers. Testosterone also augments overnight growth hormone (GH) secretion. GH is a peptide hormone, which stimulates protein synthesis and promotes lipolysis (i.e., the breakdown of fat stored in fat cells).
Another study by Bhasin and colleagues showed that testosterone therapy promotes fat loss, too. They reported that transdermal testosterone gel adminstration (10 g daily for 24 wk) in HIV-positive men with abdominal obesity and low testosterone was associated with greater decrease in body fat. This change in fat mass in the testosterone-treated men were associated with greater reductions in waist circumference and waist-to-hip ratio and in perceptions of change in abdomen size than those observed in the placebo group. There is evidence that testosterone inhibits body fat accumulation through an androgen receptor mediated pathway. That is, testosterone appears to directly promote fat loss.
Testosterone therapy has also been used to treat erectile dysfunction (ED). Testosterone is certainly vital for maintaining male secondary sexual characteristics and libido, but the direct role that testosterone has in erection physiology remains very controversial. The erect penis is the product of nitric oxide synthase producing nitric oxide (NO), which dilates blood vessels that supply the erectile tissue. Exactly how testosterone fits into this erectile physiology is unclear. Nevertheless, studies have demonstrated that around 57% of all patients who present with ED and low testosterone will respond to testosterone therapy.
Serious advserse effects associated with testostrone therapy are often related to poor quality underground products and/or inapproriate administration of the injections. However, testosterone therapy, especially in high doses, do have some well-established adverse effects, but they are largely cosmetic. Testosterone can cause alopecia (thinning of hair) and pattern baldness. Acne is also a common side effect. Significant increases in estrogen (female sex hormone) levels resulting from aromization of testosterone can cause breat enlargement (gynecomastia).
Contrary to anti-doping hyperbole, testosterone is far from Evil. It is an important contributor to the robust metabolic functioning of multiple bodily systems. Moderately high testosterone levels have numerous beneficial effects, including increased muscle mass, decreased body fat, and improved mood.
In the second part of this article, we will talk about how to increase testosterone production through diet/nutrition, training and supplementation.
Bain J. The many faces of testosterone. Clin Interv Aging. 2007;2(4):567-76.
Borst SE, Mulligan T. Testosterone replacement therapy for older men. Clin Interv Aging. 2007;2(4):561-6.
Galvao DA et al. Changes in muscle, fat and bone mass after 36 weeks of maximal androgen blockade for prostate cancer. BJU Int. 2008 Mar 10; [Epub ahead of print].
Bahrke MS et al. Psychological and behavioural effects of endogenous testosterone and anabolic-androgenic steroids. An update. Sports Med. 1996 Dec;22(6):367-90.
Allen B. Dont confuse me with the facts: Doctors have their own opinions on steroids! Mesomorphosis.com
Bhasin S et al. The effects of supraphysiologic doses of testosterone on muscle size and strength in normal men. N Engl J Med. 1996 Jul 4;335(1):1-7.
Herbts KL, Bhasin S. Testosterone action on skeletal muscle. Curr Opin Clin Nutr Metab Care. 2004 May;7(3):271-7.
Muniyappa R et al. Long-term testosterone supplementation augments overnight growth hormone secretion in healthy older men. Am J Physiol Endocrinol Metab. 2007 Sep;293(3):E769-75.
Jain P et al. Testosterone supplementation for erectile dysfunction: results of a meta-analysis. J Urol. 2000 Aug;164(2):371-5.