Testosterone is known as the primary male sex hormone as it influences the development of secondary sexual characteristics in males – such as the deepening of voice and growth of body hair during puberty.

However, testosterone is not exclusively a male hormone. It’s also required and produced by females, albeit in significantly lower amounts.

For adult men, a healthy level of testosterone is between 270 ng / dL and 1100 ng/dL, whereas a healthy level for women is between 15 ng / dL and 70 ng/dL.

Testosterone and ageing

In men, testosterone levels rapidly rise during adolescence and peak around age 20. They then remain relatively stable until around age 40. Afterwards, they start to gradually decline by about 1% per year.

Studies suggest that about 20% of men over 60, 30% over 70 and 50% of men over 80 years old have low testosterone levels.

In contrast to men, women experience much a less rapid rise in testosterone levels during adolescence. In women, as with men, levels of testosterone peak around age 20 and start to gradually slowly decline with age.

What are the health effects of low testosterone?

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1) Decreased muscle mass

Testosterone stimulates the growth of muscle. There are various ways by which it does this. Studies suggest that testosterone encourages stem cells in your body to specialise and develop into skeletal muscle cells. Testosterone also enhances the process of muscle protein synthesis.

Owing to these effects, when levels of testosterone are low, people may experience a loss of muscle mass or difficulty in building muscle.

2) Increased fat deposition

In addition to promoting muscle growth, testosterone stimulates the reduction of fat mass. There are several ways by which testosterone enhances fat loss. Testosterone inhibits the uptake of lipids by fat cells and also stimulates the breakdown of fats for energy (a process called lipolysis).

Conversely, low testosterone levels are associated with the deposition of fat, particularly around the abdominal area (a phenomenon called central adiposity) and surrounding internal organs (visceral adiposity).

Furthermore, deposition of fat tissue can lower the production of testosterone. This creates a continuous negative feedback loop, as the resulting decreased production of testosterone leads to greater deposition of fat tissue, which again decreases testosterone production further (and so on).

3) Decreased blood sugar control

Low testosterone is linked to poorer control of blood sugars. The exact mechanism by which low testosterone upsets blood sugar control remains to be fully understood. For instance, it’s unclear whether raised blood sugar levels associated with low testosterone are merely secondary to changes in body composition (lower muscle mass and higher fat mass).

Nevertheless, studies suggest that low testosterone is linked to a phenomenon called ‘insulin resistance.’ Insulin is the hormone that allows tissues in the body to take up glucose that is circulating in the bloodstream.

When tissues become less sensitive and resistant to the effects of insulin, they are less able to take up and use glucose for energy. This leads to higher levels of glucose remaining within the bloodstream. High blood glucose levels can result in cell damage,  an increased risk of metabolic disease including type II diabetes, and impaired exercise performance.

The FitnessGenes testosterone level trait

The most accurate method of measuring your personal testosterone level is a blood test, which can be obtained from a qualified healthcare professional. Analysis of genetic variants that influence testosterone production can also provide insight into whether you are at risk of low testosterone.

At FitnessGenes, we combine 11 genetic variants with relevant lifestyle factors, including age, activity level and body composition, to assess your testosterone levels.

Depending on the combination of these genetic and lifestyle factors, FitnessGenes members are categorised into one of several trait bands, ranging from ‘low genetic, lifestyle suboptimal’ to ‘high genetic, lifestyle good’. Each trait band is also accompanied by specific actions to help you increase or maintain your current testosterone production.

Discover your personal testosterone trait

Could your testosterone level be sabotaging your body composition goals, or even increasing your diabetes risk? Discover your personal testosterone production, alongside 75 other fitness-related traits with the FitnessGenes DNA analysis.

Already have genetic data from providers including 23andMe and Ancestry.com? Receive same-day access to your testosterone trait with our DNA Upload service.