Christopher Walker is a co-founder of UMZU and creator of the Thermo Diet. He is the first person to get a Duke Neuroscience degree in 3 years. After naturally solving his own health complications with a brain tumor as a teenager, he has devoted his life to creating all-natural products and education to help men, women, children and pets to improve their own health naturally using science-backed research.

Recently, a panel with cooperation from international andrology and urology societies, published specific recommendations with regard to the diagnosis of Late-onset Hypogonadism (Nieschlag et al 2005). These are summarized in the following text. It is advised that at least two serum testosterone measurements, taken before 11 am on different mornings, are necessary to confirm the diagnosis. The second sample should also include measurement of gonadotrophin and prolactin levels, which may indicate the need for further investigations for pituitary disease. Patients with serum total testosterone consistently below 8 nmol/l invariably demonstrate the clinical syndrome of hypogonadism and are likely to benefit from treatment. Patients with serum total testosterone in the range 8–12 nmol/l often have symptoms attributable to hypogonadism and it may be decided to offer either a clinical trial of testosterone treatment or to make further efforts to define serum bioavailable or free testosterone and then reconsider treatment. Patients with serum total testosterone persistently above 12 nmol/l do not have hypogonadism and symptoms are likely to be due to other disease states or ageing per se so testosterone treatment is not indicated.

There are no studies showing its effects on healthy males, but it has been shown to drastically improve testosterone in infertile males (ref 77). It's also packed full of minerals, so is a great superfood nevertheless. I use the Sunfoods brand. Make sure you buy from a quality brand, as there are a lot of poor shilajit products out there, also some have been shown to be high in heavy metals. 
This supplement contains herbal remedies to enhance the male hormone and increase a man's sexual desire. Ingredients found in the product include horney goat weed, milk thistle, tribulis terristris, wild yam, saw palmetto and maca. The manufacturer of the supplement claims that it is endorsed by a doctor for male enhancement. Recommended dosage is one capsule taken before engaging in sexual activity. Women should not take a testosterone supplement unless otherwise advised by a physician.
The researchers found that the dose of testosterone required to produce different effects in the body varied widely. The influence of testosterone and estradiol also differed. As the testosterone gel dose was reduced, the scientists showed, reductions in lean mass, muscle size, and leg-press strength resulted from decreases in testosterone itself. In contrast, increases in body fat were due to the related declines in estradiol. Both testosterone and estradiol levels were associated with libido and erectile function.
That said, a group of researchers at the National University of Malaysia did a systemic literature review of longjack, looking for clinical research that demonstrated a relationship between the shrub and testosterone levels. Of 150 articles, only 11 met their inclusion criteria — involving humans and scientifically rigorous. However, of those 11 studies, seven “revealed remarkable association” between using longjack and improving male sexual health, while the remaining four “failed to demonstrate sufficient effects.” The team concluded that longjack looks “promising” when it comes to raising low testosterone, and that there is convincing evidence that it works.
^ Jump up to: a b Sapienza P, Zingales L, Maestripieri D (September 2009). "Gender differences in financial risk aversion and career choices are affected by testosterone". Proceedings of the National Academy of Sciences of the United States of America. 106 (36): 15268–73. Bibcode:2009PNAS..10615268S. doi:10.1073/pnas.0907352106. PMC 2741240. PMID 19706398.
So, how does one ensure that testosterone levels remain in balance? Some doctors suggest that monitoring testosterone levels every five years, starting at age 35, is a reasonable strategy to follow. If the testosterone level falls too low or if the individual has the signs and symptoms of low testosterone levels described above, testosterone therapy can be considered. However, once testosterone therapy is initiated, testosterone levels should be closely monitored to make sure that the testosterone level does not become too high, as this may cause stress on the individual, and high testosterone levels may result in some of the negative problems (described previously) seen.
And remember, saturated fats work best (along with monounsaturated fats – olive oil, almonds, avocados etc.). In fact higher intakes of polyunsaturated fats (canola oil, sunflower oil, soybean oil, safflower oil, margarine etc.) are linked to LOWER testosterone levels (14 & 15). I explore the dangers of PUFA's in a lot more detail in this article - PUFA's: The Worst Thing For Your Health That You Eat Everyday.

To find the best testosterone booster, we collected every supplement available on BodyBuilding.com, and cross-checked our list against the top results on best of lists like MensFitness, BroScience, and BodyNutrition. We only looked at pills since some of the ingredients in testosterone boosters have a reputation for tasting bad, and powders just prolong the experience. There are a lot — 133 of them to be precise — and they all claim to boost testosterone levels. Testosterone (for men) is “thought to regulate sex drive (libido), bone mass, fat distribution, muscle mass and strength, and the production of red blood cells and sperm.” If a supplement can increase your natural testosterone levels, the rest should follow. As we mentioned above, it’s not that simple, and at best, you’ll experience only a short-lived boost.
Intramuscular testosterone injections were first used around fifty years ago. Commercially available preparations contain testosterone esters in an oily vehicle. Esterification is designed to retard the release of testosterone from the depot site into the blood because the half life of unmodified testosterone would be very short. For many years intramuscular preparations were the most commonly used testosterone therapy and this is still the case in some centers. Pain can occur at injection sites, but the injections are generally well tolerated and free of major side effects. Until recently, the available intramuscular injections were designed for use at a frequency of between weekly and once every four weeks. These preparations are the cheapest mode of testosterone treatment available, but often cause supraphysiological testosterone levels in the days immediately following injection and/or low trough levels prior to the next injection during which time the symptoms of hypogonadism may return (Nieschlag et al 1976). More recently, a commercial preparation of testosterone undecanoate for intramuscular injection has become available. This has a much longer half life and produces testosterone levels in the physiological range throughout each treatment cycle (Schubert et al 2004). The usual dose frequency is once every three months. This is much more convenient for patients but does not allow prompt cessation of treatment if a contraindication to testosterone develops. The most common example of this would be prostate cancer and it has therefore been suggested that shorter acting testosterone preparations should preferably used for treating older patients (Nieschlag et al 2005). Similar considerations apply to the use of subcutaneous implants which take the form of cylindrical pellets injected under the skin of the abdominal wall and steadily release testosterone to provide physiological testosterone levels for up to six months. Problems also include pellet extrusion and infection (Handelsman et al 1997).
The science backs up the soldier’s self discovery, in fact, exposure to radiation (whether it’s from an army radar or the cell phone in your pocket, or the wifi router in your house) has been shown to lower sperm quality, fertility and testosterone. This is true not only for military personnel (88, 89,90) but all males living in a modern world (91).
Have you ever wondered why? When we are under stress, our body produces cortisol that is bad for our testosterone levels. This particular component blocks the production of testosterone. In addition, if there is a lack of Z’s then this is the bad news for your testosterone. You should know that the huge amounts of testosterone are produced during our sleep. Every guy knows that the “morning wood” comes only after a good night sleep.
Bottom line: testosterone boosters aren’t right for a lot of people. We dive deep into ingredient research below, but typically, testosterone boosters contain at least one (and often three or more) different ingredients that each impact your circulatory system — both the heart and blood. If you’re taking any kind of blood-thinner medication, or you have a history of heart disease, these supplements can get really dangerous, really quickly. The simple fact of the matter is that hormones are tricky things to mess with, and a doctor should be your first port of call to help you safely achieve your goals — whether they’re related to fitness, weight, or libido.

Japanese Knotweed (a.k.a Hu Zhang or Polygonum cuspidatum) is highlighted by WebMD as needing more evidence to rate its effectiveness in a number of different areas: like treating constipation and liver or heart disease. They also warn that it can interact poorly with medications that are changed and broken down by the liver, and those that slow blood clotting (anticoagulants and antiplatelets).


I think that revamping your diet and lifestyle could be enough alone (no sugar, high fat, low carbs, lots of veggies, working out, low stress). Tongkat Ali would be an amazing added extra. I don’t know about mixing Tongkat with DAA and other stuff. Probably would be fine, but it’s strong. I usually say pick one. I know Testofuel has Fenugreek in it, but I don’t have too much experience with it. It has been proven to have effects. See this article.
Zinc is little more of a nice-to-have ingredient than a must-have. It’s on our radar as an ingredient that possibly boosts testosterone levels, and while we couldn’t find enough supporting evidence that taking zinc would increase natural testosterone, low zinc levels have been connected to infertility. A low zinc level is also possibly a sign of hypogonadism. The closest support we found is in a study which found that people recovered from nutritional deficiency-related problems more quickly if they took a zinc supplement than those who did not. Zinc is available in many foods, such as oysters, fortified breakfast cereals, and red meat.
Studies also show a consistent negative correlation of testosterone with blood pressure (Barrett-Connor and Khaw 1988; Khaw and Barrett-Connor 1988; Svartberg, von Muhlen, Schirmer et al 2004). Data specific to the ageing male population suggests that this relationship is particularly powerful for systolic hypertension (Fogari et al 2005). Interventional trials have not found a significant effect of testosterone replacement on blood pressure (Kapoor et al 2006).
Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.[46] This may be linked to the ovulatory shift hypothesis,[47] where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.
But when a premenopausal woman’s testosterone levels are too high, it can lead to polycystic ovary syndrome (PCOS), a condition that increases the risk of irregular or absent menstrual cycles, infertility, excess hair growth, skin problems, and miscarriage. High levels of testosterone in women, whether caused by PCOS or by another condition, can cause serious health conditions such as insulin resistance, diabetes, high cholesterol, high blood pressure, and heart disease. (12)
Joe Costello is a Nutrition & Wellness Consultant, certified by the American Fitness Professionals & Associates (AFPA), author, and internet blogger. Joe has more than 9 years of experience in the sports nutrition industry and over 3 years of experience as a supplement and nutrition blogger. As a certified NWC who specializes in dietary supplements, Joe strives to deliver accurate, comprehensive, and research-backed information to his readers. You can find more of Joe’s work including his E-Books about fitness and nutrition at his official website joecostellonwc.com, or connect with him on LinkedIn, Facebook, Instagram, Vimeo, or YouTube.
Levels of testosterone naturally decrease with age, but exactly what level constitutes "low T," or hypogonadism, is controversial, Harvard Medical School said. Testosterone levels vary wildly, and can even differ depending on the time of day they're measured (levels tend to be lower in the evenings). The National Institutes of Health includes the following as possible symptoms of low testosterone:
At the present time, it is suggested that androgen replacement should take the form of natural testosterone. Some of the effects of testosterone are mediated after conversion to estrogen or dihydrotestosterone by the enzymes aromatase and 5a-reductase enzymes respectively. Other effects occur independently of the traditional action of testosterone via the classical androgen receptor- for example, its action as a vasodilator via a cell membrane action as described previously. It is therefore important that the androgen used to treat hypogonadism is amenable to the action of these metabolizing enzymes and can also mediate the non-androgen receptor actions of testosterone. Use of natural testosterone ensures this and reduces the chance of non-testosterone mediated adverse effects. There are now a number of testosterone preparations which can meet these recommendations and the main factor in deciding between them is patient choice.
An international consensus document was recently published and provides guidance on the diagnosis, treatment and monitoring of late-onset hypogonadism (LOH) in men. The diagnosis of LOH requires biochemical and clinical components. Controversy in defining the clinical syndrome continues due to the high prevalence of hypogonadal symptoms in the aging male population and the non-specific nature of these symptoms. Further controversy surrounds setting a lower limit of normal testosterone, the limitations of the commonly available total testosterone result in assessing some patients and the unavailability of reliable measures of bioavailable or free testosterone for general clinical use. As with any clinical intervention testosterone treatment should be judged on a balance of risk versus benefit. The traditional benefits of testosterone on sexual function, mood, strength and quality of life remain the primary goals of treatment but possible beneficial effects on other parameters such as bone density, obesity, insulin resistance and angina are emerging and will be reviewed. Potential concerns regarding the effects of testosterone on prostate disease, aggression and polycythaemia will also be addressed. The options available for treatment have increased in recent years with the availability of a number of testosterone preparations which can reliably produce physiological serum concentrations.
Cognitive abilities differ between males and females and these differences are present from childhood. In broad terms, girls have stronger verbal skills than boys who tend to have stronger skills related to spatial ability (Linn and Petersen 1985). It is thought that the actions of sex hormones have a role in these differences. Reviewing different cognitive strengths of male versus female humans is not within the scope of this article but the idea that cognition could be altered by testosterone deserves attention.
A: Testosterone products can improve a male's muscle strength and create a more lean body mass. Typically, these effects are not noticed within the first two weeks of therapy, but it is possible that he is more sensitive and responds well to the therapy. Some of the other more common side effects of testosterone patches are headache, depression, rash, changes in libido, acne, male pattern baldness, and increased cholesterol levels. This is not a complete list of the side effects associated with testosterone patches. Megan Uehara, PharmD
In fact, high cortisol deals a crushing blow to testosterone in two ways. During, long-lasting stress, high amounts of cortisol release very often and have a direct negative influence on T levels. Thus, cortisol inhibits testosterone synthesis in the testes and hypothalamus. In addition, the production of cortisol is impossible without cholesterol. But testosterone synthesis also demands cholesterol. Since during stress cholesterol is first of all used for making cortisol, T levels simply plummet.

In order to discuss the biochemical diagnosis of hypogonadism it is necessary to outline the usual carriage of testosterone in the blood. Total serum testosterone consists of free testosterone (2%–3%), testosterone bound to sex hormone binding globulin (SHBG) (45%) and testosterone bound to other proteins (mainly albumin −50%) (Dunn et al 1981). Testosterone binds only loosely to albumin and so this testosterone as well as free testosterone is available to tissues and is termed bioavailable testosterone. Testosterone bound to SHBG is tightly bound and is biologically inactive. Bioavailable and free testosterone are known to correlate better than total testosterone with clinical sequelae of androgenization such as bone mineral density and muscle strength (Khosla et al 1998; Roy et al 2002). There is diurnal variation in serum testosterone levels with peak levels seen in the morning following sleep, which can be maintained into the seventh decade (Diver et al 2003). Samples should always be taken in the morning before 11 am to allow for standardization.
Epidemiological studies have also assessed links between serum testosterone and non-coronary atherosclerosis. A study of over 1000 people aged 55 years and over found an inverse correlation between serum total and bioavailable testosterone and the amount of aortic atherosclerosis in men, as assessed by radiological methods (Hak et al 2002). Increased intima-media thickness (IMT) is an early sign of atherosclerosis and has also been shown to predict cardiovascular mortality (Murakami et al 2005). Cross-sectional studies have found that testosterone levels are negatively correlated with carotid IMT in independently living men aged 74–93 years (van den Beld et al 2003), diabetic men (Fukui et al 2003) and young obese men (De Pergola et al 2003). A 4-year follow up study of the latter population showed that free testosterone was also inversely correlated with the rate of increase of IMT (Muller et al 2004).
Men can experience a range of symptoms if testosterone decreases more than it should. Low testosterone, or low T, is diagnosed when levels fall below 300 nanograms per deciliter (ng/dL). A normal range is typically 300–1000 ng/dL, according to the U.S. Food and Drug Administration. A blood test called a serum testosterone test is used to determine your level of circulating testosterone.
As you can see, the entire workout is only 20 minutes. Twenty minutes! That really is a beautiful thing. And within those 20 minutes, 75 percent of that time is warming up, recovering or cooling down. You're really only working out intensely for four minutes. It's hard to believe if you have never done this that you can actually get that much benefit from four minutes of exercise. That's all it is.

^ Jump up to: a b Travison TG, Vesper HW, Orwoll E, Wu F, Kaufman JM, Wang Y, Lapauw B, Fiers T, Matsumoto AM, Bhasin S (April 2017). "Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe". The Journal of Clinical Endocrinology and Metabolism. 102 (4): 1161–1173. doi:10.1210/jc.2016-2935. PMC 5460736. PMID 28324103.
Sexual arousal - boosting testosterone can improve sexual arousal, even if you have normal testosterone levels. Higher levels of testosterone can make it easier for you to get aroused and can boost your sex drive generally. While this doesn’t affect the physical action of your erections, if you are not getting hard because you’re not aroused then boosting testosterone could help.

These results have been echoed in clinical trials. A meta-analysis of 24 RCTs looked at weight loss caused by diet or bariatric surgery:[22] In the diet studies, the average 9.8% weight loss was linked to a testosterone increase of 2.9 nmol/L (84 ng/dL). In the bariatric-surgery studies, the average 32% weight loss was linked to a testosterone increase of 8.7 nmol/L (251 ng/dL).

Male hypogonadism becomes more common with increasing age and is currently an under-treated condition. The diagnosis of hypogonadism in the aging male requires a combination of symptoms and low serum testosterone levels. The currently available testosterone preparations can produce consistent physiological testosterone levels and provide for patient preference.
"The Journal of Clinical Endocrinology and Metabolism" published that males who switched from a high-fat diet to a low-fat diet also saw a decrease in their testosterone levels. If you want to put some fat back into your diet without fearing cardiac implications, plant-based saturated fat like coconut is just the ticket. Meat-based fat is also acceptable if kept to less than 10% of your dietary fat intake.

One study looking at alcohol consumption found that increasing alcohol consumption led to a higher level of free & total testosterone compared to a non-drinking control group (20). Drinking did however lower SHBG testosterone levels, though this type of testosterone is bound to a protein meaning our bodies cannot use it to build muscle or increase our mood.
The yolks of eggs exclusively are a fine source of Zinc. Egg yolks have all of the vitamins that are present in the whole egg as well. So, by consuming the yolk itself, you would get more than required fat, but you also get vitamins A, E, D and K, as well as additional amounts of minerals. Zinc and vitamin D - the pro-testosterone duo are in the captain seat in egg yolks.
The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group[186] was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",[187] and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.[188]
Testosterone is a stimulant of hematopoiesis in the bone marrow and consequently, increases the hematocrit (Shahidi 1973). Men with unexplained anemia should have their testosterone measured and if reduced, these men should be treated with testosterone. Because of the erythropoietin stimulating effect of testosterone, one of the parameters to be monitored during testosterone treatment is hematocrit since a small percent of testosterone-treated men develop polycythemia.

My educated opinion would be that it will help, but like I said I want to do some more research on the matter and I will probably end up writing a whole article on this subject, and how to reverse pufy nipples. I too have slightly puffy nipples genetically, so I have learned a lot over the years on how to reduce them and will share in an article shortly. I will message you when it is out.
^ Mehta PH, Jones AC, Josephs RA (Jun 2008). "The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat" (PDF). Journal of Personality and Social Psychology. 94 (6): 1078–93. CiteSeerX 10.1.1.336.2502. doi:10.1037/0022-3514.94.6.1078. PMID 18505319. Archived from the original (PDF) on April 19, 2009.
There are no studies showing its effects on healthy males, but it has been shown to drastically improve testosterone in infertile males (ref 77). It's also packed full of minerals, so is a great superfood nevertheless. I use the Sunfoods brand. Make sure you buy from a quality brand, as there are a lot of poor shilajit products out there, also some have been shown to be high in heavy metals. 
We start with plastic. A lot of plastic contains bisphenol A (BPA); BPA is a weak synthetic estrogen. Like many other chemicals used in making plastics, BPA is a hormone disruptor and can block or mimic hormones and how they act in the body (34). If you think you’re safe with BPA plastic, think again. Research shows that BPA free plastic has similar estrogen-like effects on the body.
^ Jump up to: a b Travison TG, Vesper HW, Orwoll E, Wu F, Kaufman JM, Wang Y, Lapauw B, Fiers T, Matsumoto AM, Bhasin S (April 2017). "Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe". The Journal of Clinical Endocrinology and Metabolism. 102 (4): 1161–1173. doi:10.1210/jc.2016-2935. PMC 5460736. PMID 28324103.
As “the ultimate guide” I want this article to be the last resource you need when it comes to boosting your testosterone. I have spent years researching this stuff, and experimenting on myself. And in case I am incomplete, I have linked out at the bottom of this page to all the best resources for increasing testosterone around the web. I truly believe there is no better resource out there than what you’re reading right now.
We kept it simple, and followed the premise of testosterone boosters: testosterone affects muscle gain, weight loss, and libido, so by increasing the amount of testosterone in the body, we can improve on each of those goals. This meant that we looked for ingredients proven to increase testosterone levels, not ingredients that might increase libido or help build muscle mass independently of testosterone (like having a healthy diet and feeling good about yourself). In addition, we dove deep into the specific ingredient lists of our finalists and cross-checked them against WebMD and the National Institutes of Health (NIH) database to make sure that they did not contain ingredients known to be harmful.

Testosterone is observed in most vertebrates. Testosterone and the classical nuclear androgen receptor first appeared in gnathostomes (jawed vertebrates).[189] Agnathans (jawless vertebrates) such as lampreys do not produce testosterone but instead use androstenedione as a male sex hormone.[190] Fish make a slightly different form called 11-ketotestosterone.[191] Its counterpart in insects is ecdysone.[192] The presence of these ubiquitous steroids in a wide range of animals suggest that sex hormones have an ancient evolutionary history.[193]


This over-the-counter supplement is intended to increase your body's level of testosterone to its highest. The manufacturer also advertises the positive effect that the drug can have on your sex life and achieving muscle growth. As a supplement, you are instructed to take four capsules each night before bed. On training days, recommended dosage is two capsules before you workout. Ingredients found in the product include tribulis terristris, long jack, maca root and epimedium.
A little goes a long way for men, but clinically many men do well with 5 to 10 mg of a topical progesterone cream at bedtime, again, only under your doctor’s supervision. Arginine is important for nitric oxide (NO) production and should be taken twice daily. I've also been recommending Testoplex™ for years. It's Xymogen’s formulation—featuring mungbean sprout powder—to address healthy testosterone levels and provide support for libido and overall vitality.
Directions — SUGGESTED USE: As a dietary supplement take 3 capsules daily, preferably with a meal, or as directed by a healthcare professional. — Take two capsules with a meal twice a day. On days that you are not training, take two capsules in the morning and two capsules at night. On days that you train, take two capsules about an hour before workouts and take two capsules in the morning or at night depending on when you train.
Try diet and exercise changes as your health permits. Losing weight, eating the right foods, and getting more exercise are great ways to naturally increase testosterone while also improving your overall health. While mild to moderate changes are likely safe in most teenage boys, you should consult your doctor before making any significant changes to make sure those changes will be right for your specific health needs.
TT may help you but it may have adverse (harmful) results. (See discussion of these side effects below.) The Federal Drug Administration (FDA) has said that testosterone drug labels should state that there is a risk for heart disease and stroke for some men using testosterone products. All men should be checked for heart disease and stroke before, and periodically while on, TT. The AUA however, on careful review of evidence-based peer review literature, has stated that there is no strong evidence that TT either increases or decreases the risk of cardiovascular events.

Christopher Walker is a co-founder of UMZU and creator of the Thermo Diet. He is the first person to get a Duke Neuroscience degree in 3 years. After naturally solving his own health complications with a brain tumor as a teenager, he has devoted his life to creating all-natural products and education to help men, women, children and pets to improve their own health naturally using science-backed research.
In 1927, the University of Chicago's Professor of Physiologic Chemistry, Fred C. Koch, established easy access to a large source of bovine testicles — the Chicago stockyards — and recruited students willing to endure the tedious work of extracting their isolates. In that year, Koch and his student, Lemuel McGee, derived 20 mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them.[179] The group of Ernst Laqueur at the University of Amsterdam purified testosterone from bovine testicles in a similar manner in 1934, but isolation of the hormone from animal tissues in amounts permitting serious study in humans was not feasible until three European pharmaceutical giants—Schering (Berlin, Germany), Organon (Oss, Netherlands) and Ciba (Basel, Switzerland)—began full-scale steroid research and development programs in the 1930s.
Present in much greater levels in men than women, testosterone initiates the development of the male internal and external reproductive organs during foetal development and is essential for the production of sperm in adult life. This hormone also signals the body to make new blood cells, ensures that muscles and bones stay strong during and after puberty and enhances libido both in men and women. Testosterone is linked to many of the changes seen in boys during puberty (including an increase in height, body and pubic hair growth, enlargement of the penis, testes and prostate gland, and changes in sexual and aggressive behaviour). It also regulates the secretion of luteinising hormone and follicle stimulating hormone. To effect these changes, testosterone is often converted into another androgen called dihydrotestosterone. 
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