Testosterone is a hormone typically found in humans and other animals and acts as the primary male sex hormone. While female ovaries also contain small amounts of testosterone, the hormone is typically found in testicles of biological male members of a species.
There are several different kinds of testosterone that exist concurrently in the male body. “Free” testosterone is a hormone that is not bound to a specific protein and is the form that has the greatest freedom to serve several functions in the human body. However, there are also forms that are bound to specific proteins, such as those bound to the blood protein albumin. The vast majority of testosterone in a man’s body is often bound to the sex hormone-binding globulin (SHBG) protein and remains inactive. (Low levels of SHGB often correlate to higher levels of free testosterone in the bloodstream.)
Another form of testosterone is dihydrotestosterone (DHT), which is produced by an enzyme in the body. This type of testosterone is chiefly used for hair growth, and skin/prostate health.
Why do we need it?
Testosterone is an androgen – an anabolic steroid hormone that regulates the development and maintenance of male sex characteristics. Testosterone is produced by interstitial Leydig cells, which are found adjacent to the seminiferous tubules in the testicles. When exposed to luteinizing hormone (LH), they produce testosterone.
When testosterone is produced, it plays an important part in the development of the male reproductive system – the testes and prostate depend on the presence of testosterone. Furthermore, testosterone is needed to synthesize and maintain muscle mass and bone density, thus staving off conditions like obesity and osteoporosis.
As such, testosterone is a vital component of many physical aspects correlated with biological maleness, including reproductive ability, physical strength, sex drive, and stronger bone mass. Higher levels of testosterone are closely associated with lower risk of heart disease, diabetes, and obesity, among other factors.
Testosterone is a key factor for the body’s control of the spermatogenic process – the means by which males produce sperm. In many cases, control of spermatogenesis is correlated with both testosterone and the follicle-stimulating hormone (FSH) in men, both being required for effective sperm production.
The body produces sperm when the brain sends a signal to the testes using gonadotropin-releasing hormones (GnRH). This signal orders the testes to synthesize more testosterone, which then results in higher sperm production.
For what it’s worth, sperm production is not significantly affected by the presence of low levels of testosterone; research indicates that some mammals with low T can still produce sperm with 5-10% levels of normal intratesticular androgen levels.
How do testosterone levels relate to age?
The amount of testosterone we produce in our lifetimes is largely correlated with age. When humans reach puberty, the endocrine system begins producing testosterone; in fact, some studies of primates have shown that early injection of testosterone in a neonatal mammal can start puberty earlier, making testosterone essential to the timely initiation of puberty.
Average testosterone decrease
per year in men after 30
As men approach middle-age, however, testosterone levels begin to lower, a process known as andropause. Studies have indicated that circulating or free testosterone slowly and steadily diminishes as men get older, with little indication of a period of accelerated drop in T levels. On average, testosterone decreases about 1% per year after a man reaches age 30 or 40, according to the Mayo Clinic.
It must be noted, however, that some studies have also seen that exceptionally healthy men did not see their T levels fall significantly with age, indicating that diminishing T levels could correlate more to age-related illnesses than age in and of itself. There are several cohort and secular effects that occur with aging – cohort effects are historical factors related to the generation each man belongs to, while secular effects are environmental in nature. Among these effects on testosterone levels include chronic illness or cumulative exposure to alcohol and tobacco over a person’s life. Chronic illness, in particular, is especially correlated to the presence of low T in older men.
What happens to our body when we don’t have it?
As our testosterone levels drop, the body characteristics that correspond with high testosterone production begin to change and level off. This includes sex drive, muscle mass, the ways in which fat is stored in the body, and more. Even direct health factors like diabetes, red blood cell production, and obesity can be affected by testosterone levels in the body.
Interestingly, according to a University of Washington study, our circadian rhythms have a curious effect on blood testosterone levels when correlated with age. In certain time-related testosterone studies, younger men were shown to have higher testosterone levels in the morning than older men, indicating that age not only plays a role in total serum testosterone levels but the time of day at which they are strongest.
Do you get more muscle with testosterone?
As an androgen, testosterone has a direct effect on muscle mass, as it promotes protein synthesis, binding with androgen receptors to stimulate tissue growth. To that end, men with higher testosterone levels experience greater strength and muscle mass, as well as higher bone density and bone strength. Combined, all of these factors contribute to the greater potential for muscle mass in a body with high levels of testosterone.
What is Low T?
Hypogonadism, which is often conflated with low testosterone levels (low T), is a clinical syndrome that results from the testis’ failure to produce sufficient levels of testosterone, as well as normal rates of sperm. Typically, this results from the disruption of one or more attributes of the pituitary, hypothalamus, or testicles.
How much testosterone should you have?
Testosterone is typically measured in nanograms per deciliter (ng/dL). Most healthy adult men with normal levels of testosterone are considered to have testosterone levels measuring between 300 to 800 ng/dL.
What happens when you fall below that range?
Men who measure below that level are considered to have Low T and display the corresponding symptoms associated with that condition.
What are the symptoms of Low T?
When men fall below the normal range of serum testosterone levels (>300 ng/dL), the following symptoms can occur, according to an Endocrine Society clinical practice guideline:
Incomplete or delayed sexual development. While most men with Low T experience symptoms later in life, there are some rare cases of younger men who experience lower testosterone levels in the neonatal stages of development. As such, delayed onset of puberty can occur, where primary adult male sex characteristics do not fully form or are delayed in forming.
Reduced sexual activity and libido. Men who have Low T often report lower levels of sexual activity, as well as a loss of sex drive.
Fewer spontaneous erections. Erectile dysfunction is often a factor as well, but other psychological factors and comorbidities can contribute greatly to that specific condition.
Gynecomastia. Gynecomastia, or enlarged breasts in men, is caused by an imbalance of estrogen and testosterone hormones, resulting in the swelling of breast tissue. While it’s not a serious condition by any means, it can lead to mild breast pain and some embarrassment.
Loss of body hair. While hair loss in men is typically more greatly related to inheritance and genetics, Low T also corresponds to a greater loss of facial and body hair.
Smaller or shrinking testicles. Testicular atrophy is a phenomenon that often occurs in men with Low T, due to the loss of germ cells and Leydig cells. Since the testicles are producing less testosterone, this results in a commensurate shrinking in size.
Low sperm count. When the body’s natural ability to produce testosterone lessens, sperm production is stunted (though not to an incredibly significant degree). Even so, it can have some marginal effects on sperm count.
Loss of height. One of the reasons boys experience growth spurts during puberty is the body’s increased production of testosterone during that time, according to a study in the Journal of Clinical Endocrinology and Metabolism. As such, male testosterone levels play a significant part in maintaining height over time. Men with Low T often experience a loss in height, as their testosterone levels can no longer support the height they were previously.
Low bone mineral density. Age-related testosterone deficiency is a significant factor in the lessening of bone mineral density among men, which results in conditions such as osteoporosis, according to this study by Universiti Kebangsaan Malaysia Medical Centre.
Sweating and hot flashes. While testosterone levels do decrease in men over time, most men still maintain a normal range throughout their lives and thus do not experience hot flashes and excessive sweating to the extent women do during menopause. However, some men with Low T, as well as most men who have undergone androgen deprivation therapy to aid them in prostate cancer treatment, experience hot flashes as a result of this hormone imbalance, according to theHarvard Medical School.
How can it affect my everyday life?
While these physiological effects can seem abstract, having Low T can take a toll on a number of practical, intrinsic aspects of one’s everyday life.
Lower energy and motivation. Men with Low T often experience a marked decrease in their overall energy levels, as well as motivation to perform everyday tasks.
Depression. Testosterone production has a marked effect on many neurobehavioral functions, according to a Columbia University study. As such, there is evidence of testosterone level’s association with symptoms of depression; androgen treatment is also suggested to improve levels of depression in older men.
Lower memory and concentration. The Harvard Medical School has found some connections between lower testosterone levels and declining memory in older men. Men with higher testosterone levels were also found to have better performance on cognitive tests.
Lack of sleep and increased drowsiness. Having low testosterone is also associated with disrupted sleep levels in many men, according to a study from the University of Adelaide. This relates closely to the aforementioned relationship between testosterone and the body’s circadian rhythms, creating a feedback loop in which older men get less sleep, which results in lower testosterone production, which then leads to even less sleep.
Mild anemia. Older adults often have a higher risk of anemia, and some studies have correlated that to testosterone deficiency in men (including this one from the Journal of the American Medical Association). As such, TRT tends to result in higher hemoglobin levels and has a high likelihood of correcting the anemia.
Lower muscle mass. Testosterone has a demonstrable effect on the presence of muscle mass, and as such its absence leads to a loss of muscle, according to this University of Rochester study. Testosterone replacement therapy, by extension, increases the synthesis of muscle proteins in older men, thus allowing them to regain muscle mass lost due to Low T.
Higher fat mass. The loss of muscle mass due to Low T matches a corresponding increase in fat mass, according to this University of Mississippi study. This also relates closely to the aforementioned prevalence of gynecomastia in men with Low T.
Diminished overall physical performance. As testosterone plays a significant role in muscle production and bone mass density, lower T levels are linked to general deficits in physical performance. Aerobic and anaerobic activity is diminished in men with Low T, though that also relates to the advanced age of many men with the condition.
What is Testosterone Replacement Therapy (TRT)?
Androgen replacement therapy, also known as testosterone replacement therapy (TRT) is a method of bolstering existing levels of testosterone in the human body. This is accomplished through a treatment regimen of diet, exercise and lifestyle changes, centered around the use of topical or injectable testosterone supplements intended to improve testosterone levels in patients.
This kind of therapy has seen a steady increase in the last couple of decades. According to the Medical Journal of Australia, testosterone use in the U.S. rose from 10.3 doses per 1,000 people in 2000 to 98.5 doses per 1,000 people in 2011.
Is it healthy?
If supervised appropriately by a wellness professional, a TRT regimen is perfectly safe for patients. However, it is recommended that clinicians do not administer TRT to patients with breast or prostate cancer, as well as people with severe urinary tract symptoms, sleep apnea, or heart failure.
What does it do?
Simply put, TRT administers additional levels of testosterone to the body’s bloodstream, compensating for the body’s lower ability to produce its own testosterone due to age or other factors. When the body’s androgen receptors have this additional testosterone to work with, the body can continue similar levels of tissue synthesis and other correlated effects as it had when the body was able to naturally produce more testosterone. The result is a higher presentation of male sex characteristics, as well as a host of other effects, due to this normalization of the body’s testosterone levels.
How does it work?
There are a number of methods for wellness professionals to administer testosterone during TRT.
Gels and Creams
Among the most common topical methods are gels and creams, which are rubbed on the body once or twice a day to allow the testosterone dosage to soak through the skin into the bloodstream. One of the most popular brands of testosterone gels is AndroGel, which studies have indicated could rapidly and efficiently increase serum T levels from low to normal rates. With daily application of between 5-10 grams of gel (which contains between 50-100 milligrams of testosterone), patients have seen efficient, safe results in higher sexual function, mood changes and more, according to a 2004 study.
Patches offer a similar form of treatment, patients applying patches containing the testosterone supplement to their body or upper arms once or twice a day. Many common transdermal T patches include Androderm, a permeation-enhanced patch with an alcohol-based reservoir, Testoderm, a patch applied to the scrotum, and Testoderm TTS, a nonscrotal patch that lacks a reservoir. Each of these is meant to deliver 5 to 6 milligrams a day of testosterone to the body, providing a low to midnormal level of the hormone to one’s bloodstream.
Studies over three to ten years of testosterone patch usage have indicated that they are effective in maintaining sexual function, as well as muscle and bone mass, in men of various ages.
However, there are some minor side effects to consider, which include a mild risk of skin irritation, and the prospect of grooming one’s scrotal hair in order to apply the Androderm patch. There are also cases of nonscrotal body patches failing to adhere perfectly in some patients.
However, the most common (and recommended) form of TRT is through injections, as the testosterone is administered directly into the muscles via syringe. The dosage then travels into the bloodstream.
Monitoring Strategies and Schedules
Many TRT regimens take place on an ongoing basis; three to six months after a TRT regimen, it is recommended that wellness professionals reevaluate the patient to see whether symptoms have responded to treatment, as well as record any adverse effects the patient is suffering from. Testosterone levels are also monitored for these patients to gauge their effects. The typical recommended T level for patients undergoing TRT is between 700 and 900 ng/dL for men receiving testosterone enanthate or cypionate.
It’s important to note that you don’t need clinically low T to benefit from TRT.
Can I rely on testosterone supplements alone?
Testosterone supplements are just one component of any normal TRT program. In addition to these supplements, wellness professionals typically prescribe a combination of diet, exercise and other lifestyle changes that further contribute to testosterone production and ensures that your body stays healthy.
What are the effects of TRT?
Copious research has been done on the effects of TRT in patients, and the prevailing body of literature on the subject is quite positive. According to this 2001 study, TRT on hypogonadal men has the effect of improving sexual function, decreasing body fat, and increasing lean muscle mass and function, as well as bone mass. Furthermore, TRT is also associated with lower cholesterol levels, higher rates of hemoglobin, and greater overall prostate health.
In studies of men undergoing TRT, the sexual function and activity levels of subjects were shown to increase more with testosterone treatment. Furthermore, testosterone treatment is also associated with increased sexual desire, as well as increased erectile function. Men also reported that sexual desire improved more frequently in the testosterone trials than equivalent placebo trials.
Erectile dysfunction is often a factor as well, but other psychological factors and comorbidities can contribute greatly to that specific condition.
Men who have undergone TRT have also reported small, if negligible, benefits in vitality, with subjects experiencing a distinct lack of fatigue compared to subjects not taking the testosterone trial.
Muscle Mass and Overall Physical Function
Testosterone replacement therapy is strongly linked to a reduction in fat mass and an increase in muscle mass, which results in more favorable body composition for physical health and psychological well-being.
Most particularly, anabolic steroids such as testosterone have been shown to increase muscle size and strength, as well as decrease fat mass, in normal men in conjunction with strength training. This correlates with the use (and abuse) of anabolic steroids in the athletic community, as supraphysiologic doses of testosterone are used to make men stronger, faster and more athletically capable.
In studies where men taking TRT were tested for physical function, there were small (if statistically negligible) improvements in walking distance, albeit greater perception of their improved walking ability.
Alleviation of Diabetes Symptoms
Men with Type 2 diabetes can also see their symptoms reduce in the wake of testosterone replacement therapy. In a State University of New York study measuring the effects of TRT on men with Type 2 diabetes, results showed that testosterone replacement was linked to lower rates of insulin resistance, as well as decreased inflammation and fat mass. Testosterone treatment was correlated with large decreases in circulating concentrations of free fatty acids, leptin, C-reactive protein, and more. This can result in much healthier outcomes for men suffering from Type 2 diabetes, both in its direct symptoms and the corresponding reduction in rates of obesity.
Higher Quality of Life, Social Status
While this effect is less explicitly measurable, the cumulative effect of the physiological and psychological benefits of TRT can lead to an overall higher quality of life and sense of well-being. Men with normal testosterone levels are more likely to feel satisfied with their appearance, sex lives, and exhibit fewer psychological conditions such as stress, anxiety, and depression.
As strange as it may seem, one study in the Journal of Personality and Social Psychology has indicated a significant correlation between testosterone levels and certain benchmarks for quality of life. For instance, one study on the relationship between testosterone, cortisol, and concrete indicators for social status found that executives with higher testosterone levels had more subordinates and higher hierarchical position in their respective organizations.
While this is certainly not a direct effect of higher testosterone levels, from a statistical level having higher T levels certainly seems to aid in one’s likelihood of achieving higher social status. The study suggests the possibility that having higher testosterone levels naturally predisposes one to seek positions of power that afford social status, as well as behaviors like confidence and dominance that correlate positively to social attainment. Higher testosterone often leads to status-promoting changes in personality including the reduction of fear, greater risk-seeking, higher desires for status and social skills. Individuals who are successful see a greater reduction in stress, which then levels off cortisol and testosterone levels, creating an “upward spiral of status attainment.”
Can You Boost Your Testosterone Naturally?
While direct administration of testosterone supplements is the most direct method of boosting low testosterone levels, it is possible to make minor adjustments to your lifestyle to help bolster your own body’s ability to naturally produce testosterone.
As with most health conditions, a healthy diet is a practical and highly recommended lifestyle change to assist in treatment. Studies have shown that diet has a tremendous impact on the body’s hormone levels, including testosterone – men who consistently overeat or diet frequently experience disruptions in their testosterone levels.
One Fitchburg State University study notes that the ideal diet for naturally boosting testosterone levels involve high levels of protein, which help to maintain healthy testosterone levels, especially as it contributes heavily to fat loss.
While carbohydrates are often discouraged in people dieting to lose weight, the presence of healthy carbohydrates in one’s diet is highly correlated with optimization of testosterone levels, particularly when engaging in a resistance training regimen.
It is also vital to balance one’s diet with plenty of healthy fats, which, as this University of Utahstudy shows, corresponds with higher testosterone levels and greater health.
Generally, it is best to focus on a balance of these three major groups, emphasizing whole foods and healthy grains, to improve overall health and bolster one’s hormone levels, including testosterone.
Sleep is a fundamental component of your body’s ability to maintain itself; concordantly, a healthy sleep cycle is strongly correlated with higher testosterone levels.
Studies on sleep and testosterone (such as this one from the University of Chicago) have found that sleeping around five hours per night can correspond to 15% lower levels of testosterone in subjects. Another U of Chicago study indicates that men who typically sleep four hours or less are more likely to have Low T. Generally, every extra hour of sleep you get strongly correlates to 15% higher testosterone levels. Men who consistently get appropriate amounts of healthy, high-quality sleep are more likely to have higher, healthy testosterone levels.
Generally, exercise is a highly recommended method for preventing many lifestyle-related diseases. However, it also has the fringe benefit of boosting your testosterone.
According to a review study at the University of Cordova, people who undertook regular exercise regimens experienced higher levels of testosterone. This is especially pronounced in the elderly, for whom exercise boosted not only their testosterone levels but their reaction time and overall fitness.
There is also literature supporting the correlation between resistance training (e.g. weight lifting) and both short-term and long-term boosting of testosterone levels. High-intensity interval training (HIIT) is particularly useful for natural increases in testosterone levels.
When combined with physical training, supplements such as caffeine and creatine monohydrate have been shown to offer potential further boosts in testosterone levels.
As obesity is a substantial predictor of lower testosterone levels, corresponding weight loss can have the effect of boosting testosterone production in the male body.
It must be stressed, however, that each of these methods provides only minor restoration of testosterone production to the male body, and merely allows the body’s own testosterone production to be as efficient as possible. Men who experience Low T and its associated symptoms should focus on starting Testosterone Replacement Therapy to restore their T levels to normal.
While insufficient scientific study has been done to conclusively support the notion of using natural supplements to boost testosterone, some research has been done on some of the more commonly used remedies. In one study from India, the herb ashwagandha was found to increase testosterone levels in infertile men, resulting in a 167% higher sperm count. Ginger extract has also been shown to increase sperm motility in animal tests, according to a study from United Arab Emirates University.
Before engaging in these herbal supplement remedies, however, it is highly recommended that you consult your physician. Otherwise, androgen replacement therapy is the most effective and reliable method of restoring testosterone levels in men.
How Do You Get Started with TRT?
In order to safely and effectively begin a TRT regimen, it is highly recommended that you seek out accredited, trusted wellness professionals to supervise your treatment.
As previously mentioned, it is extremely important to reconsider getting testosterone replacement therapy if you have prostate cancer, as well as a history of heart problems. Some studies have shown a correlation between the engagement of TRT and adverse cardiovascular incomes in older men with an existing history of heart failure, and the FDA recommends further study on this phenomenon. However, other studies (such as this one from the European Heart Journal, have shown significant reductions in myocardial infarction after the administration of TRT, resulting in a distinct lack of scientific consensus.
If fertility is a major goal for you, it is recommended that you do not seek out TRT – while testosterone is important for sperm production, it must be produced naturally by the body. Testosterone introduced from outside the body ends up suppressing the body’s own sperm production. To that end, do not seek out TRT for fertility purposes; its major application is in restoring the testosterone levels of men who wish to bolster factors like body composition and sexual performance.
Regardless of these outcomes, it is still important to talk to your physician before beginning any kind of testosterone replacement therapy regimen. They may be able to recommend wellness professionals who specialize in testosterone replacement therapy, who can then guide you through a regimen that works for your individual health goals.
This content was reviewed by Dr. Gary Kawesch. Dr. Kawesch graduated from Yale University, getting his degree in Molecular Biophysics and Biochemistry. He then got his medical degree at the UCLA School of Medicine. He completed his internship in internal medicine at USC’s Huntington Memorial Hospital in Pasadena, and his ophthalmology residency at the UCLA’s Jules Stein Eye Institute. For over 18 years, Dr. Kawesch was one of the foremost ophthalmic surgeons in the US and has consulted with and was a team doctor for seven professional sports teams in California. He continues to work with the Oakland Raiders. He trained with the American Academy of Anti-Aging Medicine and helps men increase their vitality, lifespan and overall healthspan.