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What Do I Need to Know About Testosterone?

psychiatrist, sexologist, psychotherapist
  • Published:
    11 April 2023
  • Updated:
    02 November 2023

Testosterone is the main male sex hormone that determines the development of secondary sexual characteristics, puberty, and normal sexual function in men. It is produced 90% in the testicles and 10% in the adrenal cortex.

What Determines Testosterone Levels?"

Testosterone levels depend on many factors:

  • Age.
  • Physical activity.
  • Lifestyle.
  • Diet.
  • Taking medications.
  • Sexual activity.
  • Climate.
  • Sleep.

For example, it has been proven that men in sunny countries have significantly higher testosterone levels than those in the north.

Testosterone levels in the blood serum of a healthy man vary throughout the day and follow a circadian rhythm, maximal in the early morning and minimal in the afternoon. Therefore, you should be alert if your morning erection has disappeared. 

The Significance of Total Testosterone Levels in the Body

Total testosterone levels range from 264 to 916 ng/dL (nanograms per deciliter) in non-obese European and American men aged 19 to 39. The average testosterone level in adult men is 630 ng/dL. However, the reference values in different laboratories can vary significantly, so the physician should interpret the test results.

Table of Normal Testosterone Levels in Men by Age

The level of testosterone is directly dependent on a man's age. It can be measured in ng/dL, nmol/L, or ng/mL. The table below shows the normal hormone levels for different age categories:

Age Range of Men

 Testosterone Blood Level (ng/dL)

Testosterone Blood Level (nmol/L)
0-12 months 5.76-89.34 0,2-3,1
1-8 years 1.15-3.17 0,04-0,11
9-10 years 1.15-36.31 0,04-1,26
11-18 years 1.15-628 0,04-21,8
19-30 years 151-571 5,25-19,8
30-45 years 140-493 4,85-17,1
45-55 years 123-450 4,26-15,6
55-65 years 117-401 4,06-13,9
65-75 years 100-352 3,47-12,2
75-85 years 88.76-303 3,08-10,5
85-95 years 77.52-252 2,69-8,76
over 95 years 65.99-228 2,29-7,91

The Effects of Testosterone

What is the first thing that comes to mind when we hear testosterone? Sports, muscle mass, sexual activity, aggression, and baldness. But testosterone has many more functions:

  • First, testosterone strongly affects a man's appearance, behavior, and psychological state.
  • Testosterone regulates the proper development of the prostate gland, testicles, and penis.
  • Accelerates protein synthesis (anabolic effect), promotes muscle mass recruitment, and increases strength. For example, testosterone is used by athletes to increase muscle strength and endurance. However its prolonged use results in decreased testosterone secretion, negatively affecting erections and sexual performance.
  • Controls the distribution of fat in the body so that fat is not deposited in the abdomen and thighs.
  • Increases serotonin levels, which increases mood and pain threshold. Also, the testosterone level determines men's tendency to take risks when making financial decisions.
  • It affects the hypothalamus, increasing libido.
  • Increases the level of aggression and induces a desire to compete.
  • It regulates the metabolism of phosphorus and nitrogen, which is necessary for the development of bone tissue.

Which fact about testosterone surprised you the most?

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