Testosterone plays a critical role in reproduction for both men and women. It is essential for sperm production and responsible for manly characteristics such as facial and body hair, deep voice, big muscles, and a deep ability to focus. Low levels of testosterone can impact both sperm production and sexual function. Getting testosterone tested is a critical part of any fertility evaluation. Learn more about testing options, normal testosterone levels and what to do if you find out you have low T.
What is Testosterone?
Produced by leydig cells in the testicle, testosterone is the hormone primarily responsible for sexual development and reproduction in men. Its primary role varies with age. In utero, testosterone plays a key role in the development of reproductive tissue and gender formation. Upon birth, T levels skyrocket for a weeks then drop to low levels until the onset of puberty where it kickstarts sperm production changes boys to men. It causes facial hair to grow, broadens the shoulders and crispens the jawline and is even responsible for teenage acne. T levels peak in late adolescence or early 20s and naturally decline with age.
Testosterone production is controlled by a complex chain of chemical reactions in the body known as the Hypothalamic-Pituitary-Testicular-Axis (HPTA) most easily described as the brain-ball connection. The hypothalamus senses that T levels are dropping and begins producing a hormone called GnRH. GnRH flows to the pituitary gland causing it to generate both Follicle Stimulating Hormone and Luteinizing Hormone, which in turn cause machinery in the testicle to make sperm and testosterone. A significant amount of testosterone is absorbed by sertoli cells in the testicle and is used to nourish developing sperm cells. Extra testosterone exits the tesicle into the blood stream. As testosterone levels rise, the brain stops making GnRH. Bioavailable testosterone in the blood binds to androgen receptors throughout the body to enable the production of proteins responsible masculine traits such as muscle growth and body hair production. As testosterone is used by the body, levels in the blood drop. The absence of T causes the Hypothalamus to start generating GnRH and the cycle begins again.
What is the difference between Total, Bioavailable and Free Testosterone?
As testosterone enters the bloodstream, most of it binds to a protein called sex-hormone binding globulin (SHBG). SHBG is created by the liver and plays a key role in balancing hormones. When testosterone is bound to SHBG it is unable to be used by the body. A smaller portion of testosterone generated sticks to the blood protein albumin. Testosterone stuck to albumin is still able to be used by the body. The smallest portion of testosterone in the blood stream is “free” and not bound to anything. This form of testosterone is most accessible to be used by other cells in the body.
When testing testosterone levels, doctors can used the three types of testosterone in the blood to better understand what could be causing low T symptoms. Total testosterone level is a measure of the total amount of testosterone generated by the testicle. Free testosterone is a measure of the small portion of testosterone that is floating free in the bloodstream and is not bound to any other proteins. Bioavailable testosterone is the combination of free testosterone and testosterone that is bound to albumin and is still available to be used by the body. If total testosterone is high but bioavailable testosterone is low, the doctor will know that the testicle is producing sufficient amounts of testosterone but it is not available to the body and will usually recommend different treatment options than in cases where total testosterone levels are low.
Free Testosterone: Free testosterone is not bound to any protein in the blood and is most readily available to be used by the body.
Testing options: Testosterone tests are typically ordered by doctors either to diagnose hypogonadism (low T) or as part of a fertility evaluation. Lab tests are typically performed using a blood sample that is drawn from the vein. There are a number of home tests available that either involve mailing in a sample or running a strip with saliva. If you are looking into testing yourself, make sure you are educated on the test accuracy, what form of testosterone the test is measuring and what results the test will provide. Some home tests only measure a certain type of testosterone (free, total, etc) and they have a variable level of accuracy depending on the type of technology.
What to test: It is often useful to look at other hormone levels when measuring testosterone to better understand what the body is doing. During a fertility evaluation, doctors will typically request lab results for total testosterone and FSH, the hormone that initiates sperm production. In cases of suspected hypogonadism or low T, it is useful to breakdown testosterone into total and bioavailable and get measurements for luteinizing hormone (LH) and estrodial. LH levels can help indicate if the HPTA us working properly and how healthy the leydig cells that generate testosterone are. Estrodial (a form of estrogen) is made out of testosterone. Sometimes too much Testosterone is converted into Estrodial and cause symptoms. If testosterone levels are abnormal, doctors may follow up with prolactin or SHBG.
When to test: When getting testosterone tested, it is best to go in first thing in the morning. In a normal day, hormone levels cycle from high to low. Testosterone naturally peaks first thing in the morning (partially responsible for morning wood) For this reason, doctors prefer to measure hormones between 7-10am to get a snap shot of your hormone profile when testosterone level is likely to be highest.
Things that can interfere with test results: Severe lack of sleep, heavy drinking, marijuna or opioids (including prescription pain medications) or use of testosterone, anabolic steroids or other androgens can impact testosterone levels and should be discussed with your doctor.
Normal Testosterone Range for Adult Men: 250 – 1070 ng/dL
Depending on the lab you visit the normal range for total testosterone will start anywhere from 250 – 300 ng/dL on the low end and go up to 1025 – 1075 ng/dL on the high end. Why such a wide range? Average testosterone levels vary by age. For the typical guy, testosterone peaks in the early 20’s and declines by about 1% a year starting sometime in the mid thirties. For young men, average T levels are somewhere between 600-700 ng/dL. This number drops about 50% by the time he reaches 80. Some experts have coined the phrase “andropause” to describe this natural drop in T as comparable to hormonal changes experienced by women during menopause.
How low is low?
In general, the body needs relatively small amounts of testosterone to do the essentials (make sperm, grow facial hair, etc). Men with values as low as 150 ng/dL may not experience any symptoms of low T or impacts in their fertility others may be more sensitive to drops in testosterone, especially if they’ve had significantly higher T values earlier in life. Depending on who you talk to, values from 200 – 400 ng/dL are generally considered borderline. Some men in this range experience symptoms, others don’t.
Can you have too much Testosterone?
There are relatively few medical conditions that naturally cause elevated testosterone. In rare cases, primarily benign tumors can cause testosterone levels to exceed the normal range. Typically, this is seen in younger boys and it can cause early puberty. For grown men, higher testosterone levels (when produced by the body) are associated with cardiovascular health, strong bones, improved brain function and hormone balance. However, abusing testosterone to improve looks or athletic performance can be too much of a good thing. Studies reviewing long term health effects of anabolic steroid abuse indicate increased risk of stroke, liver failure, cardiac arrhythmia and infarction. Because testosterone is converted into estrogen, elevated testosterone levels may also present symptoms associated with too much estrogen, such as gynecomastia (man boobs).
While studies have not shown a strong correlation between high testosterone levels and risk of prostate cancer, they have seen that prostate cancer treatment is more effective if testosterone is lowered. While ADT reduces tumour growth and survival, it can also increase the risk of coronary heart disease, diabetes and cardiovascular events.
What causes Low T in men?
Hypogonadism, or low T, occurs when testosterone levels drop below a certain threshold. As described above, testosterone naturally declines with age and for some men this drop can cause uncomfortable symptoms such as a decrease in sex drive, difficulties achieving an erection, trouble with focus, depression and a loss in muscle mass. Certain habits that are hard on health such as drinking, lack of exercise, chronic high stress, lack of sleep, poor diet and the like can accelerate a natural decline in testosterone and cause middle aged or even younger men to suffer from symptoms associated with low T. Researchers have also noticed that low T and obesity are linked. Gaining weight can lower testosterone levels. Lower testosterone levels can cause men to gain extra body fat — particularly in the gut. This cycle is quite literally a shot to the nuts. In cases like this, taking hard steps to lose weight can have tremendous gains as they can help boost T levels and make weight loss easier.
Severe hypogonadism (total T below 150 ng/dL) usually stems from a health condition that impacts tissues in the testicle (primary hypogonadism) or the hormones that regulate testosterone (secondary hypogonadism). In cases of severe hypogonadism, it is important to get a full workup with a urologist or endocrinologist to understand what the underlying cause is and how best to treat it. Depending on the underlying cause, there are a number of treatment options. Some treatment options may have adverse effects on sperm production, so if future fertility is a concern, men should get a semen analysis as part of the workup and discuss fertility friendly treatment options with their doctor.
Next steps: What to do if you have low T
There isn’t cookie-cutter advice for the best next steps for what men should do next if they have low T. There is a whole industry providing testosterone supplementation that promises to be a silver bullet for men suffering from symptoms associated with lowered testosterone. While TRT definitely has it’s place and can dramatically improve the quality of life of some patients, it is important to carefully consider both the root cause and future health goals. Here are a list of questions to work through with your doctor:
- What is the root cause of low T?
- Can testosterone levels be improved with lifestyle modifications?
- Do you want the possibility of having children in the future?
- Are there treatment options available that encourage the body’s natural ability to make testosterone?
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