All About Testosterone

All About Testosterone

Anil Kumar, PhD
Jul 30 2020 00:00


You will learn about: male hormone, low testosterone, low-T blood test, hypogonadism, history & properties of T, symptoms of low-T, testosterone in women, different forms of T, natural ways to boost testosterone levels, muscle strength and aging


The male hormone, testosterone, or T for short, is responsible for muscle strength and weight control in both men and women.

T in our body peaks around the age of 25-30, and then continuously declines. This age related decline is main reason why we gain weight, loose muscle strength, feel anxious and tired.

To make up for this muscle decline, athletes often abuse this hormone.

Increased weight, diabetes, and other health conditions can abnormally affect levels which can further compound these problems.

Once diagnosed, it is relatively easy to monitor and correct for low testosterone levels. A simple saliva test (with an at home testosterone test kit) that doesn’t require any needles or blood draw, can measure free testosterone levels. A men’s health test allows further understanding of key male hormones.

This article will discuss details about this key hormone, the natural decline with age, how one can test for testosterone, and how it can be maintained naturally.

What is Testosterone?

Testosterone is a hormone that both men and women produce, although we commonly associate it with male sexual health. It is responsible for muscle strength, bone mass, and fat distribution in our body, especially around the waist.

T production levels peak in youth, around the age of 25 years, before starting to decline. This decline is part of the natural aging process, falling about 1% per year as men age. Because of the important role in muscle tissue repair, it is popular among athletes to make up for the age related decline in muscle mass. Role of testosterone in athletic performance is hotly debated, especially among female athletes.

Low T levels can lead to weight gain, decreased muscle strength, anxiety, and fatigue. Among elderly, the low levels result in being ‘cranky’, disinterested, and less sociable. The increased weight, diabetes, and other health conditions can negatively affect the levels, further compounding these problems.

It is relatively easy to test for testosterone levels. An at home kit using a saliva sample can accurately determine your levels. The test measures free testosterone which is a better predictor of biologically active form in the body. The test is relatively inexpensive and one can do it from the comfort of home by shipping the samples to a lab. Besides the convenience and confidentiality it offers, the biggest advantage of the test is eliminating the need for a blood draw. That’s especially important for those afraid of needles.

Once diagnosed, it is easy to monitor and correct for low testosterone. In fact, hundreds of product are available in the market today. By 2013, estimated 2.3 million Americans regularly used them. However, there are known side effects, as the FDA warns about the risks of heart attacks and strokes associated with products used for correcting low testosterone levels.


Timeline and key events in the history of testosterone. For more, see Nature review of Testosterone: An Unauthorized BiographyRebecca M. Jordan-Young, Katrina Karkazis Harvard University Press (2019).

What are some important properties of testosterone?

  • Leydig cells in testicles and ovaries produce the male hormone
  • Testosterone belongs to the family of male hormones known as Androgens (others androgen hormones include: DHEA, Androstenedione)
  • It is a type of anabolic hormone, which promotes tissue generation by turning on genes that make muscles grow. Athletes often use it for tissue growth and recovery despite some controversy; especially useful for cancer patients & victims of starvation)
  • Testosterone is a type of steroid hormone (uses a 4-ring “steroid” nucleus backbone); other steroid hormones are: estrogen, progesterone, cortisol, Vitamin D, androstenediones, aldosterone, DHEA-S, pregnenolone
  • Derived from cholesterol

What are some important properties of testosterone?

  • Low T levels may explain the decrease in sexual drive over age.
  • Higher levels of male hormone might cause an increase aggression.
  • Low T can explain decrease in muscle size and strength, increase in body fat, and is known to contribute to fatigue and chronic tiredness.
  • Lower levels can result in thinning of bones, cholesterol problems, and high risk of heart disease – conditions that tend to increase with aging.
  • Testosterone is the ‘crankiness hormone’: low levels can affect the mood resulting in anxiety and depression, low zest for life, and reduced tendency to socialize.
  • T levels have been suspected to play a key role in family dynamics, divorce rates, crimes and social unrest.

Why is testosterone popular among athletes?

  • Androgens (or anabolic steroids) are popular among athletes for muscle build up and regular muscle maintenance.
  • Body builders take male hormone for strong muscle build up.
  • Recent studies suggest it can provide surprising boost in performance to female athletes.



    Thyroid and You – how thyroid impacts us

    All About Cortisol – latest research on the stress hormon

    All About Vitamin D – review of symptoms and impact

    CRP and Heart Risk – read about low inflammation, CRP, and risk of heart disease

What is hypogonadism or low-T problem?

  • T levels starts to drop around the age of 25, which is part of normal aging process.
  • But any abrupt drop or abnormal levels for a given age level can cause deficiency, what is known as hypogonadism.
  • There is no cure, however, a lab test and diagnosis can help understand the root cause.

What are the symptoms of low testosterone or hypogonadism?

  • The most common symptoms of low testosterone levels in men are related to reduced sexual performance (or erectile dysfunction). Although normal erection continues, it may result in low quality of sex, less frequently or one may not be able to maintain as long as before. Poor response to medications such as Viagra or Cialis may often appear as a symptom.
  • Male hormone deficiency results in decreased libido due to its impact on the brain, which regulates the sex drive.
  • Low T results in weight gain (especially around the middle) due to increase in fat & reduction in muscle mass; it also causes slower metabolism and less desire to exercise.
  • Low T may cause muscle weakness, loss of endurance and lower tendency to play sports.
  • Other symptoms include fatigue, low energy, frequently falling asleep after dinner. This fatigue can be due by low muscle strength, poor sleep, depression, and anemia — testosterone affects all these conditions.
  • Depression or anxiety, changes in mood, nervousness, and low sense of well being, higher irritability, anger, or negative thinking, poor response to anti-depressant medications, feeling terrible & no interest in life are all stereotypical characteristics of aging that match with low T symptoms in men.
  • Decreased quality of life and sense of well-being often correlate with lower levels.
  • Insomnia, that can add to fatigue is often observed.
  • Poor memory and lack of concentration–that is beyond normal age related decline–may impact work performance as a consequence of low-t.
  • Premature aging resulting in look and feel of being older than actual age often appears.


  • Male breast growth in men, especially in obese men
  • Bone problem due to thinning of bones which can result in hip, wrist or spine fracture and a strong reason for medical practitioners to recommend therapy. Since T converts to estrogen, this process needs to slow down to help bone strength.
  • Joint problems which result in aches and pains in joints.
  • High blood pressure.
  • Sensation of warmth, flashes, and excessive sweating in the night–somewhat similar to menopause.
  • Anemia due to low red blood cell production from reduced levels.
  • Decreased frequency of shaving as male hormone correlates to hair growth.
  • Loss of body hair including chest, pubic, and armpit hair.
  • Dry, flaky, and thinner skin as male hormone regulates the amount of oil produced by skin.
  • Male fertility problems, e.g., low ejaculate volume, poor sperm count as T, LH, FSH hormones hormones are needed for normal sperm production.
  • Softening or shrinking of testicles.
  • Softening of voice with more feminine sound.

What are the causes of low testosterone?

  • Most common cause of low T is the natural age related decline.
  • Trauma or injury to testicles where the hormone is produced.
  • Urological conditions that can block blood supply to cells producing it.
  • From complications of vasectomy.
  • Head injury that might affect pituitary glands.
  • Diabetes – which can both affect male hormone and can be affected by it as well. Type 1 diabetes patients generally tend to have a high rate of deficiency.
  • Combination of age-related androgen decline, excess weight, chronic illness, high blood pressure, and insulin resistance can cause a vicious cycle of low T and high blood sugar. Diabetes patients tend to have more SHBG (sex hormone-bounding globulin) that increases the bound, inactive form making the total T level normal but the free, active form may be low.
  • Obesity increases testosterone controlling hormones (leptin, cortisol, inflammatory kytokines or adipokines) that signal the brain for lower T production and thus lower muscle mass and more fat. This creates a vicious cycle of further reducing levels in body. An increased weight increases aromatose–the enzyme converting testosterone into estrogen, thus making less of the it available for muscle mass & fat control.
  • Infections of testicles (Orchitis), mumps, and HIV can cause lower T.
  • Immune system problems, such as Type 1 diabetes and autoimmune thyroid diseases attack body to reduce levels.
  • Hereditary Hemochromatosis (HH) is a genetic disorder that causes too much iron which can block pancreas and pituitary glands resulting in lower T.

  • Sarcoidosis, which are granulomas formed in the body & when formed in brain they can affect hypothalamus and pituitary gland (mostly genetic and tend to be more prevalent in African American population).
  • Alcohol is one of the most common cause of damage to testicles; tobacco, marijuana, cocaine, heroine, and narcotic medications can affect hypothalamus and pituitary gland.
  • Excess cortisol can lower the levels.
  • Fluid retention in the body can cut-off blood supply to testicles, and can result in kidney, liver, or heart problems.
  • Chronic pain increases cortisol levels and insulin resistance resulting in lower testosterone.
  • Radiation and chemotherapy can impact hypothalamus & pituitary glands.
  • Liver diseases can result in higher estrogen and thus lower T levels.
  • Exposure to female hormones, e.g., estrogen creams from spouse.
  • Any other problem related to the brain & pituitary glands.

What are normal testosterone levels in women?

T is equally important for women to maintain muscle mass, bone density, and weight control. Women have about 10 times lower levels than men. High T levels in women can result in:

  • too much facial hair.
  • increased muscle mass and low body fat content.
  • deepening of voice and smaller breasts.
  • irregular or absent menstrual cycle.
  • fertility problems, especially polycystic ovary syndrome (PCOS) that makes it difficult to get pregnant.
  • in some case, high testosterone can result in acne in women.

What are normal testosterone levels in women?

Testosterone is measured in three different forms, depending on how it binds in the blood as shown in the sketch below.


Two common measurements a lab test shows are:

  • Total Testosterone includes all the available male hormone in the body. It has three component: free testosterone (about 2%) + testosterone bound to SHBG protein (60-80%) + testosterone bound to albumin (20-40%). Whatever is bound to SHBG is not active. Therefore, total testosterone is not the best indicator of healthy levels.
  • Free Testosterone: not bound to protein & is the better indicator of testosterone levels. It is the dialyzable portion and can either be from measurement or calculation:
  • Measured free Testosterone: not bound and therefore affected by SHBG. Normally, there are two blood tests available:
  • * Equilibrium dialysis – a more accurate method for free & total T, but tends to be expensive.

    * Analog method – cheap, easy but not as reliable.

  • Calculated free T: calculated from the total T, SHBG & albumin values and sometimes more accurate than measured free T as it combines best of both worlds.
  • It is also important to understand the SHBG (Sex hormone-binding globulin) values in certain cases:

    i. if normal SHBG – total will be normal.

    ii. Is abnormal, especially low SHBG – surely there is a problem.

    iii. If high SHBG – total T may appear normal but can be low, this will need further analysis.

    The Harvard Men’s Health Watch provides an excellent description of total and free testosterone

How to get tested for low testosterone?

  • A blood or saliva sample can measure testosterone levels.
  • A saliva test is simple and less stressful than a blood test, nonetheless provides equivalent or sometimes even superior results. Saliva testing is relatively new technique and not as widely popular as blood test.
  • A saliva test measures free testosterone, the most active of the three types thus providing reliable results.
  • For blood tests, a venipuncture blood draw can cause adrenal stress in children and those afraid of needles.
  • The main concern with saliva test is variations in results. however, at-home health test from CLIA-certified labs that regularly compare their results with others can provide highly reproducible and reliable results.
  • Several scientific studies have shown saliva test can deliver equivalent and even better results. One scientific review from the journal of Clinical Chemistry confirmed these observations in 1500 males between 20 and 90 years old.
It is recommended to provide samples in the morning, around 7-10 am, within 30 minutes of waking up when the T levels are highest. One should note that testosterone is age dependent and therefore should be compared against a reference of same age group.


  • Only free Testosterone available in the saliva is tested. SHBG & albumin protein do not affect these results.
  • One needs to ensure the lab has a history of reliable testing with clearly defined ranges.
  • Such a test is not susceptible to temporary fluctuations by the stress that might appear in a blood test due to fear of needles.
  • As an example, for a 40 year male, the testosterone levels–which are highly dependent on age–will be low, normal or high if the values are:

  • 50 pg/ml or below: low levels requiring further attention (likely hypogonadism, low-t problems).
  • 50 – 185 pg/ml: normal range.
  • 185 pg/ml or above: high levels that also need attention (due to higher aggression and other concerns).


This is traditional method of testosterone testing but requires a blood draw which sometimes might show spike from stress of needles. And the ranges for a T blood test are:

  • Normal range: 260 – 1000 ng/dL
  • if < 500 ng/dL – low and may need attention
  • < 300 ng/dL – needs treatment

What are the challenges to testosterone testing?

  • Test reliability – it easier to measure high T than low T, although most people want to know if they have low levels.
  • Lab imperfections – assay variability & different reference ranges from lab-to-lab might cause variations. That’s why it is recommended to use labs that are (1) CLIA certified, (2) have a history of testing thousands of samples with well defined ranges, and (3) regularly compare their data with other labs across the country–all three conditions are met by our at-home testosterone test.
  • Hormone flexes – T is highest in the morning (one reason why men tend to get erection in the morning). If morning values are low, there is a very high chance of low T. Sometimes the recommendation is to measure 3 or 4 samples from the same day at different times for confidence.
  • Blood proteins – 98% of T is attached to proteins & only about 2% is free T, therefore any variations in these proteins might affect the results. 60-80% T is attached to SHBG and is biologically inactive, 20-40% is bound to a protein called albumin where it can become free & biologically active.
  • Variation may appear in specific individuals and due to age.
  • The blood test results may have an impact from sudden stress—from the fear of needles

What else might affect testosterone results?

It is important to know few other parameters that might affect your results:


  • It tightly binds with T (60 – 80%, which is significant).
  • Normal SHBG: is reliable for total T measurement.
  • Low or high values, means it can’t predict T accurately.
  • SHBG also increases with aging, complicating the results.


  • 20 – 40% of T binds weekly with Albumin and is bioavailable T.
  • It’s relatively less important for measurement.
  • Abnormal levels are rare.
  • It is often part of a standard blood test for metabolism.

DHT (di-hydro-testosterone):

  • Testosterone converts to DHT (by 5-alpha-reductase) – both might have impact on results.
  • It is used for high T issue diagnosis, and can result in hair loss and prostate enlargement.


  • High levels of Estrogen (and estrone & estriol) often result in low T.
  • High levels can be due to liver problems, obesity, or accidental exposure from women’s prescriptions.

Is there a diagnosis for low testosterone?

  • Medical professionals prescribe Testosterone Replacement Test (TRT) to those with low T to achieve normal levels
  • There is no pill to cure deficiency – as TRT pills cause liver toxicity,
  • Common prescriptions include gels, injections, or chewable prescriptions.
  • Low T causes lower red blood count resulting in anemia. However, TRT may sometimes cause too much blood & needs to be monitored for blood count and prostate growth.

What are the natural ways of increasing Testosterone?

  • Exercise makes muscles physically and metabolically stronger; one of the best ways to increase your levels and balance other hormones.
  • Weight training increases muscle mass and metabolism. It is the best natural way to increase levels. Medical professionals recommend 30 minutes of weight training at least twice a week.
  • Stress relief – stress lowers testosterone and other androgens. Low T slows down metabolism resulting in reduced muscle mass and increased body fat.
  • Vitamin D – although critical for bone health, it is equally important for muscles; lower Vitamin D results results in tired, flabby, and weak muscles (Vitamin D deficiency increases over age & data suggest more than half of US elders are below recommended Vitamin D levels).
  • Sleep time – our body secretes hormones while sleeping, without enough sleep body can’t produce enough.
  • Growth hormone (GH) – since GH is important for muscle growth, any deficiency will result in low testosterone symptoms.
  • Insufficient proteins – since proteins are the building blocks of healthy muscles, low protein levels in diet will impact testosterone levels.

Source: Hormone Balance by Scott Isaacs, MD


  • Learn from the experts at Mayo Clinic about Male Hypogonadism: Symptoms & causes | Diagnosis & treatment
  • Also see the Mayo Clinic’s page: Testosterone therapy: Testosterone therapy: Potential benefits and risks as you age
  • From Harvard Men’s Health Watch, read about the complexity of symptoms of low T, details on different ‘kinds’ of testosterones, what are normal testosterone levels, and how even experienced physicians have differing opinions on how to get tested for low T: Testing your testosterone: It’s tricky
  • In our review of key literature on testosterone, please also read: Testosterone vs parenting:Men’s relationship status, fatherhood, and how invested they are in paternal care significantly impact their testosterone levels
  • After testing, see your physician for next steps; there is an increased risk of heart attacks and strokes from using testosterone as outlined by the FDA Drug Safety Communication