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What Is Testosterone?

What Is Testosterone and Why Does It Decline?

Testosterone is a male hormone (androgen) made by the body. Most of the testosterone in a man’s body is produced in the testes. It’s what puts hair on a man’s chest. It’s the force behind his sex drive.

Testosterone helps:

  • Maintain reproductive tissues
  • Stimulate sperm production
  • Stimulate and maintain sexual function
  • Increase muscle mass and strength
  • Maintain bone strength

During puberty, testosterone helps build a man’s muscles, deepens his voice, and boosts the size of his penis and testes. In adulthood, it keeps a man’s muscles and bones strong and maintains his interest in sex. In short, it’s what makes a man a man (at least physically).

After age 30, most men begin to experience a gradual decline in testosterone. A decrease in sex drive sometimes accompanies the drop in testosterone, leading many men to mistakenly believe that their loss of interest in sex is simply due to getting older.

“Some say it’s just a part of aging, but that’s a misconception,” says Jason Hedges, MD, PhD, a urologist at Oregon Health and Science University in Portland. A gradual decline in testosterone can’t explain a near-total lack of interest in sex, for example. And for Hedges’ patients who are in their 20s, 30s, and early 40s and having erectile problems, other health problems may be a bigger issue than aging.”

A lot of the symptoms are mirrored by other medical problems,” Hedges says.

“And for a long time, we were not attributing them to low testosterone, but to diabetes, depression, high blood pressure, high cholesterol, obesity, and coronary artery disease. But awareness and appreciation of low testosterone has risen. We recognize now that low testosterone may be at the root of problems.”

Doctors will want to rule out any such possible explanations for symptoms before blaming them on low testosterone. They will also want to order a specific blood test to determine a man’s testosterone level. “The blood test is really the thing,” Mezitis says.


What Are Normal Levels of Testosterone?

Just like your cholesterol or blood pressure, there is a numerical range of testosterone levels (also known as T levels) that are considered normal. Low serum testosterone, also known as hypogonadism or Andropause, affects roughly 39% of men over the age of 45. Roughly 40% of men with high blood pressure and 40% of men with high cholesterol levels will have low testosterone levels. Additionally, approximately 50% of men with diabetes and 50% of obese men will have low testosterone. The prevalence of low testosterone increases with age. Researcher have found that the incidence of low testosterone increases from approximately 20% of men over 60, to 30% of men over 70 and 50% of men over 80 years of age. The brain and the testicles work together to keep testosterone within this range. When levels of testosterone are below normal, the brain signals the testicles to make more. When testosterone levels reach a normal level, the brain signals the testicles to make less. What your doctor is referencing is the range (95% of the population) for a human male (aged 20-100). Everyone gets the same range, regardless of their age.

Do I have Low T?

A.D.A.M. Questionnaire About Symptoms of Low Testosterone:

The A.D.A.M. (Androgen Deficiency in the Aging Male) Questionnaire is a basic questionnaire that can be very useful for men to describe the kind and severity of their low testosterone symptoms. The questions are as follows:

  1. Do you have a decrease in libido or sex drive? (Yes or No)
  2. Do you have a lack of energy? (Yes or No)
  3. Do you have a decrease in strength and/or endurance? (Yes or No)
  4. Have you lost height? (Yes or No)
  5. Have you noticed a decrease “enjoyment of life”? (Yes or No)
  6. Are you sad and/or grumpy? (Yes or No)
  7. Are your erections less strong? (Yes or No)
  8. Have you noticed a recent deterioration in your ability to play sports? (Yes or No)
  9. Are you falling asleep after dinner? (Yes or No)
  10. Has there been a recent deterioration in your work performance? (Yes or No)

(Please Note: If you answer yes to questions number 1 or 7, or if you answer yes to more than 3 questions, you may have low testosterone levels and may benefit from testing and low T treatments.)



When you look at each of the signs and symptoms individually, you may not think they point to Low Testosterone. That’s because they may be difficult to tell, and may in fact be caused by other medical conditions. Check out the Low Testosterone signs and symptoms below to see if any of them apply to you:

  • Sexual dysfunction (difficulty obtaining and maintaining an erection)
  • Fatigue
  • Reduced sex drive (reduced sexual activity)
  • Decreased energy
  • Loss of body hair, reduced shaving
  • Depressed mood
  • Increase in body fat
  • Decrease in bone strength
  • Reduced muscle mass
  • Difficulty sleeping
  • Poor concentration
  • Worsened cholesterol levels
  • Decreased motivation

Reduced Sex Drive
Low Testosterone can cause low libido (decreased sex drive), which is a lack of desire for sex that may lead to reduced sexual activity.

Decreased Energy
Some men may think loss of energy is just a part of aging. However, it may not just be a sign of getting older – low energy may also be a symptom of Low Testosterone. Some men with Low Testosterone may experience daily fatigue. Men who lack energy due to Low Testosterone may even find it difficult to do routine tasks, like mowing the lawn. If you have Low Testosterone, you may find it harder to feel like exercising. It’s not just about having low energy; Low Testosterone can cause some men to feel tired and sleepy during the day when previously they would have been awake and on the go. If you don’t have the same energy you used to and you have some of the other symptoms listed here, you may have low testosterone.

Body Changes
If you have Low Testosterone, you may have noticed changes in your body. Testosterone helps increase muscle mass and strength, and maintain bone strength. Low Testosterone can also cause other body changes like increased breast size, loss of body and facial hair, and decreased bone density (osteoporosis). Men who have osteoporosis are more prone to fracture. If you’re noticing more fat and less muscle mass along with other symptoms of low testosterone, you may have Low Testosterone.

Mood Changes
Changes in mood can be a symptom of Low T. Some men who have Low Testosterone may experience depressed mood or increased irritability.

Sexual Dysfunction
If you’re having difficulty maintaining erections, it may be more than erectile dysfunction (ED). For some males, it may be a sign that they have Low Testosterone. 

Low Testosterone 
A man’s interest in sex, as well as the ability to perform sexually may be effected by low testosterone

Are There Any Health Risks Associated With Low Testosterone?

Researchers are uncovering more and more about testosterone and how it connects to men’s health.  Through this research they have been able to connect the dots between certain health conditions and the low testosterone levels. Some of the major health problems that have been tied to low testosterone are, obesity, high blood pressure, diabetes, and metabolic syndrome. Low testosterone isn’t the known cause for the health issues, and testosterone therapy isn’t the cure. However, there is a link between the two and studies have shown health improvements for men who have taken testosterone replacement. The association of certain medical conditions and low testosterone are very interesting and worth looking into.Here is a list of some of the common health problems tied to low testosterone:

  • Diabetes
  • Obesity
  • Hypertension
  • Aging
  • High Cholesterol


Know Your T Number

Go For Optimal, Not Average.

If your testosterone level falls within the ‘normal range’ it only means that your reading falls within the range of 95% of the male population between the ages of 20 and 100. This includes all males regardless of their health. Everyone gets the same range, regardless of their age. Instead of average we should strive for ‘optimal’. By falling within the average readings, it’s safe to say only that you have ‘average’ amounts of Testosterone in your system. But we don’t want to go for just ‘average’, we want optimal testosterone levels so that we can derive as much benefit as we can from this virile molecule.

What’s an optimal T level, you ask? Great question!

The answer is: “It depends.”

First, we want to see how our number compares with other healthy males of the same age. Then we want to strive for the 95th percentile. Our target should be a reading that is higher than 95% of all males in your age group, regardless of their health.

Second, we want to feel great. Every man is different, so their level of optimal testosterone will be different, too. For some men, a testosterone level of 600 ng/dl will make them feel great, while other men need to be around 800 ng/dl in order to experience the benefits of optimal Testosterone. If you feel great with a reading at the 80th percentile then that is fine for you.

Clinical research still has not determined a hard threshold level for when symptoms of low T begin appearing. For some men the symptoms of low testosterone might begin appearing in men when their total testosterone level dips below 800 ng/dl, while other men might start noticing low testosterone symptoms when their total testosterone dips into the 400s.

Testosterone Level (ng/dl)

Age Group Average Total T Lowest 10% Top 95%
25-34 617 388 1,000
35-44 668 380 940
45-54 606 350 890
55-64 562 330 880
>65-74 524 237 790
75-84 471 <200 695
>85-100 376 <200 542