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What is testosterone?

5 min read

Testosterone is one of the most important hormones in your body. All people have it, even women, although men have far higher levels. Produced in the testes, testosterone affects far more than just your fertility. It can be responsible for changes in your libido, metabolism, bone structure and even your mood!

So, what is testosterone?

Testosterone is a hormone, which means that it is one of the body’s chemical messengers, travelling from the testes to other parts of the body to promote healthy function. 

It is produced naturally in the body when a  hormone from the pituitary gland is sent to the testes. In a cell called a Leydig cell, testosterone is then produced, before entering your bloodstream. Your body is really clever – using a feedback mechanism, it monitors the level of testosterone in your blood to make sure that your pituitary gland is telling your testes to make the right amount.

What does testosterone do?

In men, testosterone is produced in the testicles and is most well-known for its impact on sexual function. In puberty, for example, testosterone is responsible for some of the changes that men go through, including, bone and muscle development, enlargement of the penis and testicles, facial hair growth, and voice changes.

But, outside of this, testosterone plays an important role in many other important processes in your body. Mood stability, metabolism, maintaining muscle strength, fertility and bone structure, meaning that it can play a major role in your overall health, and quality of life. 

Natural testosterone levels

For men, testosterone levels vary from individual to individual, and also change over your lifetime. Testosterone levels also fluctuate throughout the day: it is highest in the morning, and then drops as the day progresses. It should be measured between 7–11 am and should 

Over a lifetime, the amount of testosterone a man’s body produces changes. It slowly increases until a man reaches puberty, and then peaks in his 20s. From the age of 40, naturally occurring testosterone levels begin to drop by about 1-2% per year. There are other, external factors that can impact a man’s level of testosterone. Taking certain types of medication, such as steroids or opioids, can cause low testosterone. More generally, overall health and lifestyle can impact testosterone production,  especially health conditions such as obesity, diabetes, kidney and liver disease, and other chronic illnesses. 

Symptoms and treatments for low testosterone

Low testosterone, also known as hypogonadism, comes with a series of symptoms. If you have low testosterone, you may experience only a few of them or all of them. If you think you have low testosterone, it’s important that you speak to your healthcare provider to get tested. Or, order an easy, at-home test kit and speak to one of our friendly experts.

The symptoms include:

  • Erectile dysfunction

  • Delayed puberty

  • Small testes

  • Infertility

  • Decreased sexual desire and activity

  • Decreased frequency of sexual thoughts

  • Erectile dysfunction

  • Delayed ejaculation

  • Decreased volume of ejaculate

  • Decreased or absent morning or night-time erections

  • Loss of muscle and strength

  • Increased body fat

  • Loss of body hair, including in the armpit and pubic regions

  • Unstable moods (eg anger, irritability, sadness, depression)

  • Sleep problems

  • The inability to concentrate is sometimes called ‘brain fog’ 

  • Decreased well-being or poor self-rated health 

  • Decreased cognitive function (including impaired concentration, verbal 

  • Memory and spatial performance)

During treatment, careful follow-up ensures that testosterone levels are too high. The result of taking too high a dose of prescribed testosterone, or the overuse of anabolic steroids leads to symptoms such as :

  • Acne

  • Enlarged prostate

  • Gynecomastia (male breast tissue growth)

  • Sleep issues

  • Fluid retention

  • Testicular shrinkage

  • Low sperm count

  • Increased number of red blood cells, called erythrocytosis

Luckily, there are a number of options for treating low testosterone levels. If you are worried that you are experiencing low testosterone, speak to one of our doctors today to start your treatment journey.

Written by Ted’s Health and medically reviewed by Professor Mike Kirby