Testosterone: The Male Hormone and Its Functions
Published: 28 April, 2025 | 10'
Sex hormones play important roles in the body, both in men and women. They are responsible for the development of the reproductive organs during adolescence and are in charge of regulating the reproductive cycle throughout our lives.
In the case of male sex hormones, they are produced in the testes and are responsible for the process of sperm production. The group of male hormones is called androgens and is regulated by the endocrine system. We refer to the main and most well-known of all: testosterone.
What is testosterone and why is it so important?
Testosterone is a hormone in the group of androgens and is one of the most important in men. It is produced in the testes and influences numerous processes that go far beyond sexual desire and reproduction, such as the maintenance of the musculoskeletal system, the production of white blood cells and sperm, the production of body hair, mood, and cognitive functions, among others.
During fetal development, around week 7, sexual differentiation associated with testosterone production begins due to the presence of the Y chromosome. In childhood, it is produced in small amounts, and it is from around the ages of 11-13 that the puberty stage begins, when the brain (pituitary gland) stimulates the production of testosterone in higher quantities that peak during adulthood, before declining in later years.
Despite what many believe, testosterone is not exclusive to men, as it is also present in the ovaries of the female reproductive system, although in very small amounts.
Functions of testosterone in the body
Coinciding with the high production of testosterone during puberty, one of the main functions of this hormone is growth and development at a physical level, although it is involved in many other processes throughout life.
Development of male sexual characteristics
The increase in testosterone is responsible for physical changes in the male body throughout its life cycle. It contributes to the development of both internal and external reproductive organs, along with other male-specific characteristics such as facial and body hair, a deep voice, and also changes in fat distribution.
Sperm production and fertility
It is during adolescence that sperm begins to be produced in a process called spermatogenesis, and thus, male fertility appears. Testosterone is the main hormone for sperm formation, although other hormones such as follicle-stimulating hormone, luteinizing hormone, and inhibin are also involved.
Regulation of sexual desire or libido
Testosterone is a key hormone in libido, both male and female, and is responsible for regulating sexual desire as the presence of this hormone is directly related to a greater sexual interest. Additionally, it stimulates the production of dopamine, one of the neurotransmitters responsible for emotional well-being, but also for sexual motivation. Likewise, it helps maintain erectile function and promotes blood flow in the genital area.
Maintenance of muscle and bone mass
Sex hormones play an essential role in the maintenance and growth of the musculoskeletal system. Specifically, in the bone realm, testosterone is involved in the production of osteoblasts, cells responsible for bone formation, and helps with bone mineralisation and maintaining its density.
It also participates in protein synthesis, aiding in the increase of muscle mass and maintaining it in optimal conditions, as well as muscle hypertrophy, a process of increasing strength and muscle growth. This, in turn, has beneficial effects on physical performance and aids in recovery after physical exercise.
Influence on mood and mental health
Besides having effects on the physical body, testosterone influences the nervous system regarding cognitive function, behaviour, and mood. Thus, it is involved in the production of hormones that affect mood such as dopamine and serotonin, as previously mentioned, and directly impacts the expression of behaviours related to dominance or competitiveness, although at higher levels it can increase aggressiveness.
Similarly, optimal levels of testosterone are associated with improved attention and memory processes, preventing cognitive decline.
Testosterone levels
Testosterone levels vary throughout life, primarily dependent on age, but also on other factors such as lifestyle, certain medical conditions, and hormonal changes.
Normal testosterone ranges in men and women
Testosterone is measured in nanograms per decilitre (ng/dL) and its values can be known through a hormonal blood test.
During childhood, approximately until the age of 10, the values in both sexes are similar, ranging from 1 to 8 ng/dL. From adolescence onwards, they start to increase and range between 300-1,000 ng/dL in men and between 9-60 ng/dL in women from the age of 18.
How levels vary with age
As previously noted, testosterone levels begin to significantly rise in males from puberty. They typically reach their peak between the ages of 20 and 30 and thereafter decline by around 1-2% per year. This explains why testosterone levels in older ages are lower, leading to physical and mental changes such as loss of muscle mass or cognitive decline.
Additionally, throughout the day, testosterone levels fluctuate and are usually higher in the morning and drop at night.
In women, peak levels are also reached around the age of 20 and begin to gradually decline. During pregnancy, the presence of testosterone supports the development of the male reproductive system in fetuses. Later, in the premenopausal stage, testosterone produced in the ovaries is higher than oestrogens and progesterone compared to older ages during menopause when these hormones begin to decrease and are no longer produced.
Factors influencing testosterone production
Testosterone production varies depending on various biological factors as well as lifestyle-related factors.
As mentioned earlier, age is a determining factor in testosterone production, although genetics also plays a role, and any physical imbalance in both testicular function and the hypothalamus, which regulates production processes, can influence it.
Regarding lifestyle, nutrition is also crucial since certain nutrients such as magnesium, zinc, or vitamin D are necessary for testosterone production, as well as healthy fats. Conversely, excessive alcohol consumption and other habits like smoking are negative.
Engaging in physical exercise and ensuring sufficient rest also have positive effects, while sleeping less than 6 hours and stress can reduce testosterone levels.
Symptoms of low testosterone, what is hypogonadism?
Testosterone can vary due to various causes, as previously discussed throughout the life cycle of both men and women, but a sustained deficit of this hormone can also occur, known as hypogonadism. This may be due to genetic disorders, infections, trauma, or other conditions such as the use of certain medications.
The symptoms of low testosterone or hypogonadism include:
- Decreased libido.
- Erectile dysfunction.
- Fatigue.
- Loss of muscle and bone mass.
- Infertility.
- Mood changes.
- Increased body fat.
Additionally, a delay in puberty with a consequent slow growth of the testes or penis, and even lack of voice deepening and body hair, can also be determined by low testosterone levels.
Fatigue, lack of energy, and mood changes
Since testosterone is related to energy metabolism, muscle mass, and mood, low levels can affect the sensation of fatigue and lack of energy. It is also associated with increased feelings of stress and decreased motivation.
Decreased sexual desire and erectile dysfunction
In turn, fatigue and changes in mood can affect libido and decreased sexual desire, but can also have physiological effects such as erectile dysfunction.
Muscle mass loss
As testosterone levels progressively decline with age, there is also a loss of bone density and muscle mass, affecting both men and women. As a result, there is a greater risk of osteoporosis, lower physical performance, and decreased strength.
High testosterone: What are the consequences?
Likewise, high testosterone levels can cause changes in various areas such as mood, sexual function and libido, muscle mass and body hair in both sexes, although with characteristics unique to each sex.
Effects of elevated testosterone levels in men
In the case of men, high testosterone may manifest physically with acne or excessive sweating, as this hormone is involved in the production and secretion of fat.
An increase in irritability or aggressiveness may occur in relation to mood swings, and it can also impact sexual desire and function, leading to difficulties with erections, as well as a reduction in semen quantity and libido. Changes in body hair may also occur, with excessive growth on the body and/or the onset of early baldness on the head.
High testosterone in women, what happens in the body?
High testosterone levels in women also impact the same areas, although with peculiarities. For example, in terms of body hair, excessive growth may also occur, but in atypical areas for women such as facial hair.
In terms of sexual function, it affects sexual desire, but may also lead to vaginal dryness or irregular menstrual cycles, and even physical changes in the vulvar area such as an enlarged clitoris.
How to maintain normal testosterone levels
As we've seen, testosterone influences numerous internal processes, so it's important to maintain optimal levels through a healthy lifestyle. This can be achieved with a proper diet, regular exercise, a correct nighttime rest routine, and learning to manage stress.
Nutrition
What we eat affects testosterone production, just like it does with other hormones.
There are key nutrients that promote the maintenance of normal testosterone levels, such as vitamin D, magnesium, zinc, or omega 3 fatty acids. Additionally, consuming healthy fats can help maintain a balance in hormone levels. We can find these nutrients in foods such as fatty fish (salmon or sardines), shellfish, leafy green vegetables (spinach or kale), dark chocolate, and eggs, among others.
Thus, it is advisable to follow a balanced diet that includes proteins, healthy fats, and carbohydrates as a foundation for good overall health, avoiding restrictive diets or, on the contrary, overeating.
The role of dietary supplements
A healthy diet can be complemented with dietary supplements. Ingredients such as maca, tribulus, or ginseng can help promote hormonal balance, especially being useful in the sexual life.
It is important to emphasise that any symptom associated with a hormonal imbalance should be consulted with a healthcare professional to determine the origin of the situation and the measures to address it.
Physical exercise: strength and endurance training
Regular exercise is one of the best ways to take care of our overall health. Our physical activity also influences hormone production, such as testosterone, although its effects vary depending on the type of exercise and its intensity.
For instance, there are studies that have examined the variation in testosterone levels in endurance exercises such as weightlifting, which reveal an increase in this hormone both in the short and long term, as well as in high-intensity interval training or HIIT. In both cases, this increase in testosterone primarily occurs in men.
Healthy habits: sleep and stress reduction
Getting good sleep is almost as important as a proper diet and exercising and also influences our hormone production. In adulthood, it is recommended to maintain a stable routine of night rest of at least 7-8 hours per day. So much so that a study conducted at the University of Chicago in 2011 (Leproult, et al), revealed that sleeping only 5 hours a night is related to a reduction in testosterone levels.
Just as occurs with a disturbance of sleep, long-term stress influences our internal processes and can elevate cortisol hormone levels, which in turn can reduce levels of other hormones like testosterone.
Myths and truths about testosterone
Around the production of hormones, there is a variety of information, although not all of it is backed by scientific evidence. Testosterone has often been associated with some myths, such as the idea that it is only found in men, or that low levels only affect sexual performance. Let's look at some of the most common questions surrounding this hormone.
Does more testosterone mean more strength?
Testosterone does influence muscle strength development, as it contributes to protein synthesis and muscle tissue formation, although high levels do not necessarily always correlate with strength gains.
There are other factors related to muscle strength such as the type of training, nutrition, and genetic predisposition of each person; testosterone alone will not generate more strength without this combination.
At what age does testosterone decline?
As we've seen throughout the article, testosterone reaches its peak between the ages of 20 and 30, and begins to naturally decline from that age. The rate at which it decreases varies according to genetics and lifestyle factors. Stress, imbalanced sleep and nutrition routines, sedentary behaviour, or obesity can accelerate this process.
Is low testosterone dangerous?
Testosterone levels vary depending on age, genetic factors, and lifestyle; however, low levels over an extended period can have significant consequences physically and mentally. It may lead to a loss of muscle and bone mass, increased fat accumulation, feelings of fatigue and lack of energy, low mood, and decreased libido, affecting sexual function.
It is advisable to consult a healthcare professional regarding these symptoms in order to carry out necessary checks and find the origins, which may relate to this hormone or other causes.
If you want to know more about male health...
Content reviewed by the specialists of the Scientific Information area of MARNYS. This article is informative and does not replace a consultation with a specialist.
