The Complex World of Testosterone

cerascreen GmbH

The Male Sex Hormone

Testosterone is the most important male sex hormone as it is crucial for many developments and processes in the male body. Women also use testosterone in their bodies, though to a lesser extent than men. With increasing age, the body’s production of testosterone decreases more and more. According to a study, 20 - 40 % of men suffer from testosterone deficiency beginning around 40 to 50 years old. Apart from decreasing muscle power, hair loss and changes in libido, low testosterone has considerable impact on health. Testosterone also plays an important role in physiological processes: Various metabolic processes like development of the body and even blood formation depend on testosterone. Apart from the gender-specific physiological functions, the effects of testosterone are of particular interest to athletes.

This article guides you through the complex world of testosterone. We provide a detailed definition of testosterone and explain the importance of balanced testosterone levels, especially for the male body. We explain the negative impact of a testosterone deficiency on your body, on your performance and on your libido. We'll also cover excess testosterone and how it unbalances the body and has negative effects. We give you tips on how to increase testosterone values naturally. On the basis of recent studies, we describe the topics sports, cardiovascular diseases, hair loss and prostate cancer in a comprehensible manner.

Very important: This article is not only addressed to the male reader. Testosterone is also vital for female health!

What is testosterone?

Testosterone is the most important male sex hormone (androgen). It belongs to the steroid hormones and has build up (anabolic) effects in the body. It is responsible for sexual desire (libido), sperm production and the growth of the external sex organs. Women also produce testosterone in small quantities. [1]

Good to know: In men, 90 % of testosterone is produced in the testicles and women, in the ovaries. In addition, low production takes place in the adrenal cortex.[1]

Why your body needs testosterone

The term "male sex hormone" is a bit of a misnomer as small quantities are also present in the female body. The accumulation of the (anabolic) steroid hormone influences various functions in both sexes:[1]

  • physical build and body development
  • building of muscle mass
  • increases the fat-free muscle mass in the body
  • development of secondary sex characteristics (in the womb)
  • sperm production in men
  • libido enhancer
  • bone stability and bone growth
  • body hair
  • blood formation
  • lowers the lipid content

Good to know: The hormone values in men can be ten times higher than in women. Therefore, the much higher concentration of this hormone in men is one of the reasons why men have a higher muscle percentage than women. In contrast, the female sex hormone estrogen increases the fat percentage in the body.[1]

Testosterone Deficiency

During puberty, testosterone is produced in considerable quantities. It is responsible for the growth of pubic and body hair (like beard and chest hair). Testosterone production in men declines with age due to physiological causes. In women, the level is less depending on age, however it also decreases over time.[1]

Studies have shown that 20 - 40% of men by age 40 to 50 suffer from testosterone deficiency.

Many of the affected men only notice it when symptoms/complications of testosterone deficiency occur. Timely measuring of testosterone levels in the body provide early diagnosis of declining testosterone levels so appropriate measures can be taken.[2]

Testosterone Deficiency - Symptoms

Symptoms of testosterone deficiency range from decreasing muscle power, reduced physical performance, osteoporosis, depressive mood, increased production of abdominal fat tissue, hair loss, anaemia, high blood sugar values to diabetes and increased libido (erectile dysfunction) as well as reduced sperm quantity in men.[3]

Testosterone Deficiency - Causes

Reasons for low testosterone levels in men and women can be:

  • obesity
  • severe malnutrition
  • severe chronic diseases
  • chronic stress
  • inflammations
  • major/serious operations
  • alcohol or drug abuse
  • Addison’s disease with too low cortisol levels
  • liver cirrhosis
  • long-term use of cortisone and hormone preparations[1]

Testosterone Deficiency = Menopause?

Due to the prevalence of testosterone deficiency in men, the existence of male menopause, the so-called andropause, is a possibility. However, unlike in women, only one in ten men is affected.[1]

Especially in women, menopause and hormonal contraceptives can lead to low testosterone levels. Ovarian sub-function (ovarian insufficiency) and therapy with drugs, like anti-androgens, can also induce testosterone deficiency.

In men, hypofunction of the gonads (e.g. Klinefelter’s-syndrome) or misuse of anabolic steroids can lead to low testosterone values.[1]

Good to know: Antiandrogens are drugs used to reduce the production of male sex hormones. They are used for treatment of prostate cancer, skin diseases and increased body hair in women. Moreover, they are contained in birth control pills.[4]

Testosterone Deficiency In Young Men

Low testosterone levels are seldom in men under 30 years of age. If, however, a testosterone test determines too low blood levels, these can be caused by:[5]

  • high cholesterol levels
  • high blood pressure
  • overweight
  • alcohol and drug abuse
  • anabolic steroids
  • various diseases like e.g. Addison’s disease

Sometimes young people experience testosterone deficiency, however, there is no need to worry. Low testosterone levels at very young age can occur if puberty and hormonal change starts late. It's normal that the beginning of puberty varies from person to person.[6]

Use of Anabolic Steroids and Its Side Effects

Anabolic steroids are substances which influence the body’s protein synthesis whereby growth processes in the body are accelerated. This can lead to increase in muscle growth, however, the use of anabolic steroids is afflicted with harmful side effects:[7]

In men: Abuse of anabolic steroids decreases natural production of testosterone in testicles and adrenal cortex. After ending of the use of anabolic steroids, natural production of hormones does not continue immediately. This leads to reduced sperm count, growth of the breast and testicular shrinkage.

In women: The use of anabolic steroids leads to so-called “masculinization” with male hair growth, disorders of the menstrual cycle and deepening of vocal tones.

Further side effects: Due to the muscle building properties of steroids, all muscles of the body are growing which leads to the life-threatening enlargement of the heart. The influence of excess testosterone is also apparent in lipid metabolism. The lipids shift from the so-called “good” HDL cholesterol towards the “bad” LDL cholesterol. This can lead to arteriosclerotic deposits and its consequences (thrombosis, heart attacks, strokes and liver damages). Psychic changes and mental dependence are also possible results of anabolic steroid abuse.[1]

Good to know: Due to enormous side effects of anabolic steroids, the Olympic Committee prohibited testosterone already in 1976.[1]

Conclusion: Anabolic steroids have a negative impact on hormone production which can lead to testosterone deficiency in men. The side effects for women include increase in body hair and complications in hormonal balance. The risk of cardiovascular heart diseases and mental illnesses in both genders increases as well.[1]

Testosterone Deficiency – Treatment

Drug therapy to treat low testosterone levels caused by a disease must, of course, be supervised by a doctor. Continue reading to learn how you can raise your testosterone levels naturally.

10 Natural treatments for low testosterone levels

Testosterone levels cannot be raised by prescribed drugs alone. There are various other factors that can boost testosterone production:

1. Sports: Weight training stimulates testosterone production. Short interval training has a positive effect on testosterone production. Extremely long endurance sessions, however, lead to a decrease of testosterone levels.[8]

2. Sufficient sleep: During sleep, testosterone is produced and enough sleep reduces stress (cortisol).[9]

3. Reduce cortisol: The more stress hormones are present in the body, the less testosterone is available. Cortisol is the antagonist of testosterone.[8]

4. Reduce excessive weight: Overweight men often have low testosterone levels. Studies indicate the following: The thicker the stomach, the lower your testosterone level. Also, fatty tissues actively produce hormones, but the wrong ones!

5. Vitamin D: Studies show a correlation between vitamin D and testosterone production. After the intake of vitamin D, increased testosterone values were measured.[11]

6. Zinc: Various studies proved the increase of testosterone levels after improvement of zinc levels. Zinc lowers estrogen levels which instead increases testosterone levels. Moreover, it reduces cortisol levels which also leads to more testosterone.[12]

7. Magnesium: According to several studies, the intake of magnesium also leads to increased testosterone levels. When you do sports on top, this further increases testosterone levels.[13]

8. Selenium: Optimize your selenium levels! Also here, studies show that the intake of selenium (in case of a deficiency) increases testosterone levels.[14]

What all three minerals and vitamin D have in common: Test first, then supplement!!

9. Avoid alcohol and nicotine: Alcohol increases cortisol levels. Smoking lowers testosterone levels.[15]

10. High-fiber diet: Too high insulin levels lead to reduced testosterone levels. Therefore, foods that cause the blood glucose levels to rise sharply should be eaten less. These include: white sugar, white bread, fruit juices and highly processed foods. Whereas complex carbohydrates are beneficial for a lower increase of blood sugar levels. These can among others be found in whole-grain products, legumes, high-fibre fruit and sweet potatoes.[16]

Intermittent Fasting To Increase Testosterone Levels

Recent studies proved that intermittent fasting can increase the body’s testosterone production by 200 percent. Intermittent fasting is an umbrella term used for various diets that cycle between a period of fasting and non-fasting. The most popular method is the 16:8 method. This means you are fasting for 16 hours each day and only eat during the remaining 8 hours, typically on the same schedule each day. For example, you can eat between 12:00 noon and 8:00 p.m. Two meals are advised which at best correspond to the above recommendation. From 8:00 p.m. to 12:00 noon the next day you are fasting. Don’t worry, during this time you don’t die of thirst! Within these 16 hours you are allowed to drink - fresh water, unsweetened drinks, juice drinks or tea. Further positive effects are attributed to intermittent fasting.[17]

Normalizing Testosterone Levels in Case of Basic Diseases

Basic diseases that cause critically low testosterone levels must, of course, be treated under doctor supervision. Testosterone levels are raised by anabolic steroids (= synthetic testosterone analogues).

Good to know: One of the relevant basic diseases is the so-called hypogonadism, which occurs most often in older people. It is treated by hormones prescribed by a medical specialist in the form of tablets, injections or special patches. Synthetic testosterone analogues are chemically modified so that their effect as a sex hormone is reduced.[18]

Testosterone - Tablets
If low testosterone levels are measured and natural treatment is insufficient, a testosterone treatment is prescribed and supervised by a doctor. Testosterone can be prescribed in the form of tablets or injections. Injections need to be administered by a doctor. Every two to four weeks, 200 mg are injected. Oral drugs have a lower dosage. Tablets contain about 20 mg testosterone. During treatment, testosterone levels should be controlled regularly to adapt the dosage accordingly.[19]

Excess Testosterone

The intake of testosterone (e.g. anabolic steroids) can lead to excess testosterone. Side effects in both men and women are not to be underestimated. Long-term consequences of anabolic steroids cannot be excluded. In general, it is not advisable to supplement testosterone without diagnosis. Otherwise, there is an increased risk of strokes. Studies observed the following side effects in study participants that supplemented testosterone though their hormone levels were sufficient: Acne, enlarged prostate and sleep apnoea (a temporary suspension of breathing during sleep).[5, 20, 21]

Conclusion: Testosterone should only be supplemented if a too low testosterone level was diagnosed.

Excess Testosterone Levels – Symptoms

Both men and women have testosterone in their bodies. In both genders, excess testosterone leads to different symptoms.

High Testosterone Levels – Causes

Testosterone levels in men and women can be too high when testosterone is supplied ‘from outside’ i.e. in the form of tablets, injections etc. (for example through doping drugs) or in case of a tumor of the adrenal gland. Cushing’s disease - which causes increased cortisol levels - can be another cause. In women, ovarian cysts and ovarian tumors as well as congenital hormone disorders of the adrenal cortex (adrenogenitale syndrome); in men, active testicular tumors can raise testosterone levels.

Good to know: Defective androgen receptors can be another reason for excess testosterone. Receptors are protein complexes that bind signaling molecules to start certain reactions. Androgen receptors bind androgens such as testosterone to start the necessary reactions which influence masculine appearance and behavior.[22]

Elevated testosterone levels in women cause disorders of the menstrual cycle, involuntary childlessness and hirsutism (typical male body hair) with acne and hair loss as well as masculinization. In men, the symptoms correspond to those of abuse of anabolic steroids.

High Testosterone Levels – Treatment

As excess testosterone is mostly caused by a disease, the underlying disease has to be treated. These diseases may be Cushing’s disease and tumor diseases, however there are others as well. Treatment is based on drugs such as glucocorticoids, which are used mainly for Cushing’s disease. Women with too high testosterone values mostly are prescribed birth control pills which inhibit the body’s testosterone production.[19]

Testosterone – Values

Testosterone levels are highest in young adults and slowly decrease as of the age of 30 which is a natural change of the blood levels. According to studies, the value decreases by one percent every year. Therefore, you should keep an eye on your testosterone levels and not take testosterone tablets just by chance.[5]

Athletes should aim at higher levels as testosterone improves performance and stimulates protein metabolism for muscle growth.[8]

Testosterone Levels - Chart

Hormones are subject to natural fluctuations. Therefore, no fixed reference value can be given. Instead, the blood levels should stay within a natural range. The following table shows you the normal ranges of testosterone values. The span of the optimal range in men is much bigger than in women as men have a lot more testosterone in their bodies than women.[23]

We created the following table as a guide. It shows the values measured in healthy men:

Testosterone values change with age as the hormone production decreased as of the age of 30. Therefore, the range of measured values decreases from age group to age group.

Testosterone – Test

As of the age of 30, it is advisable for men to test their testosterone levels. As mentioned before, the body’s own production decreases with age: The risk of testosterone deficiency increases and various symptoms occur, which complicate everyday life. The female gender is also not spared from testosterone deficiency. Also in women, deficiency of the male sex hormone can lead to specific symptoms.

Good to know: It is not recommended to treat your testosterone levels simply out of fear of deficiency. Excess testosterone can lead to health problems and mostly indicates an underlying disease so you should always see a doctor for medical diagnosis and supervision.

What’s a testosterone test?

A testosterone test is used to determine your current testosterone levels. Testosterone is bound to certain proteins in blood and unbound (= active form) in saliva. Depending on the test, testosterone is either measured in your saliva or blood. It makes more sense to measure the active testosterone in saliva. The active form can be used completely by the whole body in contrast to the bound testosterone.

Some drugs (hormone preparations) influence the result, which must be taken into account for the measurement. The following graphics show a list of drugs which should be paused latest 4 days prior to the test execution (but please consult your physician first):

The cerascreen® Testosterone Test

The cerascreen® Testosterone Test is suitable for both men and women. The test measures the active form of testosterone in saliva. The test kit includes the equipment necessary for testing. For the analysis of your testosterone levels, you only need to fill three tubes with a small amount of saliva after getting up. Then you send the samples to our certified laboratory. After analysis, you receive a result report with comprehensive information and individual recommendations.

Use the test to achieve clarity about your testosterone levels and to protect your cardiovascular system.

How long does the testosterone test take?

The testosterone test is neither time-consuming nor complex. The cerascreen® Testosterone Test requires three saliva samples:

  • right after getting up
  • 30 minutes after getting up
  • 1 hour after getting up

The saliva samples are sent to our specialist laboratory and evaluated by experts. Just a few days later, you receive the result report with comprehensive information.

The cerascreen® Testosterone Test in brief:

  • determination of the level of free testosterone in your saliva
  • sample taking from the comfort of your home
  • three saliva samples are needed
  • analysis of free testosterone in saliva with meaningful parameters
  • you receive a comprehensive result report with individual recommendations

Which doctors can do a testosterone test?

Should you be interested in an analysis of your testosterone levels by a doctor, please consult your family doctor. Apart from family doctors, you can also consult medical specialists such as urologists, endocrinologists or andrologists. Andrologists deal with male health, particularly relating to the problems of the male reproductive system, in which testosterone plays an essential role.

A personal interview about your medical history helps to clarify whether certain drugs are taken which influence testosterone metabolism. Furthermore, you are checked for the presence of acne, hair loss, body weight change and they examine your breast tissue. Women are checked for the presence of strong body hair. On the basis of your symptoms, the doctor normally takes a blood sample for analysis of your testosterone levels.

Testosterone and Weight Reduction

A multitude of studies currently evaluate hormones which play a role in weight reduction. One of the hormones, testosterone, also seems to play a major role in carbohydrate, fat and protein metabolism.

In protein metabolism, testosterone assures the production of proteins from the different amino acids. This confirms the role of this steroid hormone in muscle growth. Furthermore, testosterone in carbohydrate metabolism assures sugar (glucose) metabolism. In lipid metabolism, the hormone is contributing to the energy supply from fatty acids.[1]

Scientific Findings

Overweight people especially often suffer from testosterone deficiency. With increasing numbers of people who are categorized as overweight and obese, the risk of deficiency rises up to 75%. Studies show that hormone treatment in testosterone deficient patients - no matter which overweight rate they have - leads to weight loss WITHOUT a yo-yo effect. Apart from weight reduction, the hip circumference was also reduced.[24–26]

Conclusion: In summary, it can be said that overweight people are a risk group for testosterone deficiency. It makes sense to rebalance testosterone values to reduce weight. It is not advisable to take testosterone supplements out of pure suspicion. Arbitrary supplementation may lead to a surplus. Hormonal balance reacts very sensitively to fluctuations which is why the surplus of a single hormone leads to further discrepancies in the entire system. Currently, a correlation between too high testosterone levels and high blood pressure, as well as heart attacks and strokes, is being discussed. In order to avoid arbitrary supplementation, the testosterone test can be used to provide evidence on the actual testosterone levels.

Testosterone and Sports

In sports, various training goals can be pursued. Weight loss, endurance, muscle building and muscle definition are only some of the key factors to take into account in training. The anabolic hormone testosterone helps to increase your personal performance and to reach your goals and deficiency of this hormone can hamper the attainment of these objectives.

Testosterone and its Muscle-Building Effects

Testosterone is an anabolic steroid hormone. This means that it contributes to anabolic processes such as muscle growth. The steroid hormone stimulates the formation of muscle fibers and the production of proteins. Protein formation - thus the linking of several amino acids - is among others controlled by testosterone.[1]

Scientific Findings

During strength training, more testosterone is produced. Therefore, athletes mostly have higher testosterone levels than non-athletes. Moreover, it was found that testosterone levels in men increase sharply if their opponents have an appearance of confidence. This stimulates ambition which in turn increases hormone levels.[1]

Conclusion: You should carefully track your testosterone levels if you want to optimize performance. Competing in sports itself can help raise testosterone levels. However, only strength exercise helps, whereas endurance sport has opposite effect.

Testosterone and Cardiovascular Diseases

With increasing age, the risk of cardiovascular diseases rises. Testosterone levels also change. This is why scientists assume a correlation between testosterone levels and cardiovascular diseases.[27] Below, we explain how far testosterone and diseases of the cardiovascular system correlate.

There are several risk factors for the occurrence of cardiovascular diseases. These include smoking, elevated blood lipids (cholesterol), high blood pressure and diabetes mellitus. These factors cause an increased deposit of plaque on the vascular walls (arteriosclerosis). The thicker the plaque gets, the more the blood vessel gets clogged up until they are blocked completely. This condition may result in heart attacks or strokes.

Testosterone's General Impact on Cardiovascular System

Testosterone is proven to have an effect on the heartbeat, for example by influencing muscle growth. Studies determined decreased blood pressure in case of optimal testosterone levels which in turn reduces the risk of heart attacks.[27]

In a study conducted in 2014, scientists also determined improved blood sugar and cholesterol values through optimization of testosterone levels.[10]

Conclusion: Optimal testosterone values can help to reduce three out of four risk factors for cardiovascular diseases.

Testosterone and Hair Loss

Men with bald head or increasing hair loss (which can also affect women) can be caused by increased testosterone levels. Testosterone is transformed in the prostate and is present in skin, hair roots and the prostate. The androgen hormone dihydrotestosterone is, above all, associated with hair loss. However, genetics is paramount with regard to hair loss. If the hair roots are sensitive due to genetic disposition, dihydrotestosterone has an aggressive effect on the hair roots. This leads to severe hair loss.[28]

Conclusion: Hair loss occurs if the hair roots are sensitive to dihydrotestosterone

Testosterone and Prostate Cancer

According to recent studies, testosterone treatment does not increase the risk of prostate cancer and that relevant fears are unjustified.[29]

Testosterone treatment can, however, lead to prostate enlargement which above all affects the bladder. However, the enlargement is not equivalent to a cancerous disease.[5]

Conclusion: Treatment which includes large quantities of testosterone does not increase the risk to develop prostate cancer.


  • Testosterone is the primary male sex hormone. However, women also have testosterone in their bodies.
  • Testosterone is an anabolic steroid hormone which has cumulative effects and is produced in considerable quantities during puberty.
  • Its functions include the appearance of visible gender characteristics, sperm formation, development of physique and muscles.
  • As of the age of 30, testosterone production decreases.
  • Symptoms of testosterone deficiency are:
    Lethargy, depression, decreased libido, osteoporosis, acne and hair loss.
  • Deficiency reasons can be:
    Chronic diseases, inflammations, overweight and drug abuse.
  • Testosterone levels can be raised by:
    Medicines, sports, weight reduction, vitamin D supplementation and a balanced diet rich in fibers, magnesium, zinc and selenium.
  • Testosterone supplementation should not take place without medical supervision and authorization!
  • Excess testosterone can be caused by doping, Cushing’s disease as well as tumor diseases and can lead to symptoms such as infertility, enlarged sex organs, hair loss, severe body hair, acne and mood swings.
  • Optimal testosterone levels have positive effects on the risk of cardiovascular diseases and athletic performance.

Reference list

  1. Heinrich, P.C., Müller, M., Graeve, L., Löffler, G., Petrides, P.E. eds: Löffler/Biochemistry and Patho-biochemistry. Springer, Berlin Heidelberg (2014)
  2. Testosterone,
  3. Grober, E.D.: Testosterone deficiency and replacement: Myths and realities. Canadian Urological Association Journal. 8, 145 (2014). doi:10.5489/cuaj.2309
  4. Peter Nuhn: Natural Products Chemistry. S. Hirzel Verlag, Stuttgart
  5. Testosterone therapy: Potential benefits and risks as you age,
  6. TTFB - Clinical: Testosterone, Total, Bioavailable, and Free, Serum,
  7. Pschyrembel Online | Anabolic Steroids,
  8. Wood, R.I., Stanton, S.J.: Testosterone and sport: current perspectives. Horm Behav. 61, 147–155 (2012). doi:10.1016/j.yhbeh.2011.09.010
  9. Wittert, G.: The relationship between sleep disorders and testosterone in men. Asian J. Androl. 16, 262–265 (2014). doi:10.4103/1008-682X.122586
  10. Traish, A.M.: Testosterone and weight loss: the evidence. Current Opinion in Endocrinology, Diabetes and Obesity. 21, 313 (2014). doi:10.1097/MED.0000000000000086
  11. Pilz, S., Frisch, S., Koertke, H., Kuhn, J., Dreier, J., Obermayer-Pietsch, B., Wehr, E., Zittermann, A.: Effect of vitamin D supplementation on testosterone levels in men. Horm. Metab. Res. 43, 223–225 (2011). doi:10.1055/s-0030-1269854
  12. Chang, C.S., Choi, J.B., Kim, H.J., Park, S.B.: Correlation between serum testosterone level and concentrations of copper and zinc in hair tissue. Biol Trace Elem Res. 144, 264–271 (2011). doi:10.1007/s12011-011-9085-y
  13. Maggio, M., De Vita, F., Lauretani, F., Nouvenne, A., Meschi, T., Ticinesi, A., Dominguez, L.J., Barbagallo, M., Dall’aglio, E., Ceda, G.P.: The Interplay between Magnesium and Testosterone in Modulating Physical Function in Men. Int J Endocrinol. 2014, 525249 (2014). doi:10.1155/2014/525249
  14. Shafiei Neek, L., Gaeini, A.A., Choobineh, S.: Effect of zinc and selenium supplementation on serum testosterone and plasma lactate in cyclist after an exhaustive exercise bout. Biol Trace Elem Res. 144, 454–462 (2011). doi:10.1007/s12011-011-9138-2
  15. Haugvad, A., Haugvad, L., Hamarsland, H., Paulsen, G.: Ethanol does not delay muscle recovery but decreases testosterone/cortisol ratio. Med Sci Sports Exerc. 46, 2175–2183 (2014). doi:10.1249/MSS.0000000000000339
  16. Grossmann, M., Panagiotopolous, S., Sharpe, K., MacIsaac, R.J., Clarke, S., Zajac, J.D., Jerums, G., Thomas, M.C.: Low testosterone and anaemia in men with type 2 diabetes. Clin. Endocrinol. (Oxf). 70, 547–553 (2009). doi:10.1111/j.1365-2265.2008.03357.x
  17. Ho, K.Y., Veldhuis, J.D., Johnson, M.L., Furlanetto, R., Evans, W.S., Alberti, K.G., Thorner, M.O.: Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 81, 968–975 (1988)
  18. Zitzmann, M.: Hypogonadism in men - diagnosis, therapy, aspects of onset of action and course of therapy in testosterone substitution. 13
  19. A Harvard expert shares his thoughts on testosterone-replacement therapy,
  20. Chung, K.-J., Kim, K.-H.: Forbidden fruit for athletes, but possible divine blessing for rehabilitation: testosterone. J Exerc Rehabil. 11, 2–4 (2015). doi:10.12965/jer.150191
  21. Gruenewald, D.A., Matsumoto, A.M.: Testosterone supplementation therapy for older men: potential benefits and risks. J Am Geriatr Soc. 51, 101–115; discussion 115 (2003)
  22. Androgen Receptor Structure, Function and Biology: From Bench to Bedside,
  23. Faller, Adolf; Schünke, Michael: The human body - introduction to construction and function. Thieme
  24. Saad, F., Haider, A., Doros, G., Traish, A.: Long-term treatment of hypogonadal men with testosterone produces substantial and sustained weight loss. Obesity (Silver Spring). 21, 1975–1981 (2013). doi:10.1002/oby.20407
  25. Haider, A., Yassin, A., Doros, G., Saad, F.: Effects of Long-Term Testosterone Therapy on Patients with “Diabesity”: Results of Observational Studies of Pooled Analyses in Obese Hypogonadal Men with Type 2 Diabetes,
  26. Yassin, A., Doros, G.: Testosterone therapy in hypogonadal men results in sustained and clinically meaningful weight loss. Clin Obes. 3, 73–83 (2013). doi:10.1111/cob.12022
  27. Ayaz, O., Howlett, S.E.: Testosterone modulates cardiac contraction and calcium homeostasis: cellular and molecular mechanisms. Biology of Sex Differences. 6, 9 (2015). doi:10.1186/s13293-015-0027-9
  28. American Hair Loss Association - Women’s Hair Loss / Causes of Hair Loss,
  29. Morgentaler, A., Traish, A.M.: Shifting the paradigm of testosterone and prostate cancer: the saturation model and the limits of androgen-dependent growth. Eur. Urol. 55, 310–320 (2009). doi:10.1016/j.eururo.2008.09.024