Testosterone

Geschatte leestijd: 5 minuten Testosterone plays an important role in muscle mass. This hormone is often colloquially referred to as the male hormone because it is responsible for many characteristics that are characteristic of men. Testosterone is responsible for sperm production, deepening of the voice, beard growth, and of course muscle growth. Because of this positive influence on muscle growth, there are many different synthetic forms of this hormone available in the form of steroids. In this article, we want to delve a little deeper into testosterone and muscle growth.

Function of testosterone

As mentioned in the opening of this article, testosterone is responsible for a number of “male” characteristics. Naturally, men have a higher amount of testosterone in their bodies than women and a production that is on average 20 times higher [1,2,3]. For women, testosterone is mainly important as a “precursor” of estrogen, the “female” hormone into which testosterone can be converted. Testosterone primarily does its work via the so-called androgen receptor in the cell. Receptors can be seen as proteins in the cell membrane, cytoplasm, or cell nucleus that can transmit messages from signal molecules. Testosterone is such a signal molecule, and via the androgen receptor, testosterone leads to the release of signals to and within the cell that lead to the production of proteins that build the components of muscle fibers.

Testosterone Production

As mentioned, both women and men produce the hormone. It should be noted that men and women also produce the female hormone, estrogen. A balance of these hormones is found in the body: men have more of the male hormone and women have more of the female hormone. In the diagram next to this, you can see the production in men. HPTA stands for hypothalamic–pituitary–testicular-axis, the cooperation between the hypothalamus, the pituitary, and testes. In the diagram next to this, you can see the steps that lead to the production and release of testosterone by the testes. Testosterone itself is formed from cholesterol, like other steroid hormones. In the diagram above, you can see this production of steroid hormones from cholesterol, but also processes such as the conversion into estrogen and dihydrotestosterone [4].

Anabolic and Androgenic

Testosterone is an anabolic androgenic steroid. It has anabolic properties and androgenic properties. Anabolic refers to the fact that your body switches to the mode of creating tissue, in the case of testosterone muscle tissue. Androgenic refers to the fact that it enlarges “male characteristics,” such as body hair, facial hair, and aggression.

Total Testosterone and Free Testosterone

There should be a distinction made between total testosterone and bioactive testosterone. The largest part of testosterone, about 60%, is bound to sex hormone-binding globulin (SHBG). In men, this is also called testosterone-binding globulin. Additionally, a smaller portion is bound to the protein albumin, about 38%. Only the remaining approximately 2% is unbound. It used to be thought that only this unbound portion was bioactive and caused the results mentioned above. However, it is now known that even the part bound to albumin can easily detach to become active and have an effect [5]. More important than the total amount of testosterone is therefore the amount of the portion that is not bound to SHBG. However, the total level does provide a good indication of this, especially when also looking at the levels of luteinizing hormone and follicle-stimulating hormone.

Normal Testosterone Levels (Total)

There can be significant differences in testosterone levels between different people of the same sex and similar age. However, these should fall within a certain range. According to the Mayo Clinic, these are the values ​​within which your testosterone level should be based on gender and age [mayo].

Total Testosterone Standard Values

Age:	T Level (ng/dL):	Age:	T Level (ng/dL):
0-5 months	75-400	0-5 months	20-80
6 mos.-9 yrs.	<7-20	6 mos.-9 yrs.	<7-20
10-11 yrs.	<7-130	10-11 yrs.	<7-44
12-13 yrs.	<7-800	< strong>12-16 yrs.	<7-75
14 yrs.	<7-1,200	17-18 yrs.	20-75
15-16 yrs.	100-1,200	19+ yrs.	8-60
17-18 yrs.	300-1,200
19+ yrs.	240-950
Avg. Adult Male	270-1,070	Avg. Adult Female	15-70
30+ yrs.	-1% per year

Bioactive Testosterone (Free Plus Albumin Binding) Standard Values

Men

• < or =19 years: not established
• 20-29 years: 83-257 ng/dL
• 30-39 years: 72-235 ng/dL
• 40-49 years: 61-213 ng/dL
• 50-59 years: 50-190 ng/dL
• 60-69 years: 40-168 ng/dL
• > or =70 years: not established

Women

• < or =19 years: not established
• 20-50 years (on oral estrogen): 0.8-4.0 ng/dL
• 20-50 years (not on oral estrogen): 0.8-10 ng/dL
• >50 years: not established

Circadian Rhythm of Testosterone

Testosterone levels change throughout the day and night. In addition, you can see an example of the circadian rhythm of testosterone. Therefore, measurements are usually consistently made in the morning between 07:00 and 10:00. If you want to know what effect this can have on training performance at different times of the day, also read the article “Training in the Morning or Evening”.

Use of Anabolic Steroids

Above, we have seen normal values. The use of anabolic steroids can cause increases far above these values. A value higher than 50% of the top of the normal range is generally considered to indicate the use of externally introduced testosterone derivatives. The positive influence of testosterone on muscle growth is also well known in the sports world. Thus, increasing muscle size often leads to better performance, which is why testosterone-enhancing agents are often used in sports. As you can see in the diagram, the increase in testosterone leads to the hypothalamus producing less GnRH (Gonadotropin Releasing Hormone). This then causes the pituitary to produce less luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Reduction of these leads to a decrease in production by the testes. This can lead to the mental and physical problems that can occur when ending a steroid cycle. This is attempted to be counteracted by the use of substances used as Post Cycle Therapy (PCT) such as Clomid and Nolvadex. Other problems arise from the conversion of testosterone to estrogen (aromatase), which can lead to fluid retention and female breast formation in men (gynecomastia). This is attempted to be counteracted with aromatase inhibitors. Above, you have seen normal testosterone levels. In a study conducted by Victor Conte for his company BALCO, the testosterone levels of 24 IFBB pro bodybuilders were measured. On average, they had a level of 3100 ng/dl, more than three times the top value of adult men. Additionally, there were men with very low levels because they had previously done a cycle that stopped/suppressed their own production. One bodybuilder had a level so low that it could not be measured. This was compensated for by another bodybuilder with a level of a whopping 21,000 ng/dl. Yes, you read that right. Although BALCO is not directly synonymous with credibility due to the doping scandals surrounding ZMA, I see no reason to doubt this data. It says nothing about testosterone values ​​of “an average user” because there is no such thing. However, it does say something about the possible large differences compared to natural values.

Use of Testosterone in Women

If women are administered artificial testosterone, the effects are different than when this is done in men. Women who use steroids often experience masculinizing effects alongside the desired effect of muscle growth. For example, women can develop a deep voice and even experience facial hair growth. In addition to these side effects, steroids in women can also lead to mood swings, aggression, menstrual disorders, and a broad jawline. In extreme cases, you even see a growing clitoris in women who have used steroids.

References</ strong>

1. Torjesen PA, Sandnes L (Mar 2004). “Serum testosterone in women as measured by an automated immunoassay and a RIA”. Clinical Chemistry 50 (3): 678; author reply 678–9.
2. Southren AL, Gordon GG, Tochimoto S, Pinzon G, Lane DR, Stypulkowski W (May 1967). “Mean plasma concentration, metabolic clearance and basal plasma production rates of testosterone in normal young men and women using a constant infusion procedure: effect of time of day and plasma concentration on the metabolic clearance rate of testosterone”. The Journal of Clinical Endocrinology and Metabolism 27 (5): 686–94.
3. Southren AL, Tochimoto S, Carmody NC, Isurugi K (Nov 1965). “Plasma production rates of testosterone in normal adult men and women and in patients with the syndrome of feminizing testes”. The Journal of Clinical Endocrinology and Metabolism 25 (11): 1441–50.
4. Peter Bond. Bond’s Androgene Anabole Steroïden. Proefdruk
5. Manni A, Pardridge WM, Cefalu W, et al: Bioavailability of albumin-bound testosterone. J Clin Endocrinol Metab 1985;61:705
6. mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/83686
7. E. Nieschlag, H. M. Behre . Male Reproductive Health and Dysfunction. Springer-Verlag Berlin Heidelberg GmbH
8. t-nation.com/supplements/testosterone-production-the-elemental-facts