Causes of low testosterone in young men

Do you often feel persistently fatigued, lack motivation, or simply not like yourself? While stress and a busy lifestyle are common suspects, the underlying cause for some young men may be low testosterone. Although testosterone deficiency is often considered an issue that arises later in life, it can occur much earlier and have a significant impact on energy levels, mood, muscle development and even fertility. It is therefore essential to understand the role of testosterone, recognise the signs of deficiency, and know how to address it, in order to maintain long-term health and wellbeing.

Table of Contents

• What is testosterone and why is it important?
• What are normal testosterone levels?
• Common causes of low testosterone in young men
• Signs and symptoms of low testosterone
• When to see a doctor
• Tips for supporting healthy testosterone levels
• Summary

Research on low testosterone in young men is limited in Europe, but available data show it is not uncommon. About 2% of men overall have low testosterone, with prevalence rising to over 8% in those aged 50-79 (Cleveland Clinic, 2022). U.S. data from more than 4,000 men aged 15-39 found that around 20% had testosterone deficiency, with average levels declining sharply between 1999 and 2016 (Patel, P., et al., 2020). Although exact figures for the Netherlands and Germany are lacking, these findings show that low testosterone can affect men of all ages, including younger men with certain risk factors.

What is testosterone and why is it important?

Testosterone is a sex hormone, produced mainly in the testes in men and in smaller amounts in the ovaries in women. The adrenal glands also contribute indirectly by producing dehydroepiandrosterone (DHEA), a hormone that the body can convert into testosterone and estrogen. Specifically in men, testosterone plays a vital role in:

• Development of male internal reproductive organs (fetal development)
• Development of male external reproductive organs (fetal development)
• Increase in height (puberty)
• Body and pubic hair growth (puberty)
• Enlargement of penis, testes, and prostate gland (puberty)
• Increased libido / sex drive (puberty & adulthood)
• Production of sperm (adulthood)
• Stimulation of red blood cell production (adulthood)
• Maintenance of bone strength (adulthood)
• Maintenance of muscle strength (adulthood)
• Support of overall well-being (adulthood)

Source: Cleveland Clinic, 2022

What are normal testosterone levels?

Below you can find the optimal testosterone levels for males: 

Note: Reference ranges can differ slightly depending on the lab. Only a healthcare professional can interpret results in the context of symptoms and overall health.

While levels naturally fluctuate, persistently low testosterone in younger men may signal an underlying medical condition or lifestyle factor that requires attention.

Source: Cleveland Clinic, 2022

Common causes of low testosterone in young men

Although testosterone naturally fluctuates throughout life, persistently low levels in young men are often linked to a variety of lifestyle, medical, genetic, or treatment-related factors:

1. Lifestyle and Environmental Causes

• Obesity / Excess body fat: Higher body fat is strongly linked to lower testosterone in men (Ma, H., et al., 2024). A study with young men aged 18-30 with moderate to severe obesity (BMI > 32.5), found more than 60% to have low testosterone (Shah, S. S., et al., 2024).
• Diet: Clinical trials show that low-fat diets can significantly reduce total and free testosterone in men, compared to diets with adequate healthy fats (Whittaker, J., & Wu, K., 2021).
• Sleep restriction: Just one week of <5 hours of sleep per night can reduce testosterone by 10-15% in young healthy men (Leproult, R., & Van Cauter, E., 2011).
• Endocrine-disrupting chemicals (EDCs): Exposure to EDCs (such as those found in plastics and pesticides), has been linked to lower testosterone levels, although human evidence is still mixed (Rodprasert, W., et al., 2021).

2. Medical & Health Conditions

• Pituitary or hypothalamic disorders: Problems in the brain’s hormone centers (the hypothalamus or pituitary gland) can block the signals that tell the testes to make testosterone, leading to central hypogonadism (Pivonello, R., et al., 2017).
• Chronic illnesses (e.g. cancer): Low testosterone is common in men with cancer and in cancer survivors, which can be caused both by the illness itself and by treatments such as chemotherapy, radiation, or surgery (Xu, P., et al., 2021).  

3. Genetic / Developmental Factors

• Klinefelter syndrome (XXY): It’s estimated that around 65-85% of men with Klinefelter syndrome have low testosterone (White, J. T., 2022). 

4. Medication & Treatment Side Effects

• Chemotherapy or radiation therapy: Can damage testosterone-producing cells. Low testosterone is common in testicular cancer survivors as a result (Walsh, J. S., et al., 2019).
• Substances (e.g. opioids): Research shows that 20-80% of men who use opioids long term develop low testosterone (Kafel, H., et al., 2025).

Signs and symptoms of low testosterone

Low testosterone in young men may cause:

• Reduced sex drive
• Erectile dysfunction
• Loss of armpit and pubic hair
• Shrinking testicles
• Hot flashes
• Low or zero sperm count (azoospermia), leading to infertility
• Depressed mood
• Difficulties with concentration and memory
• Increased body fat
• Enlarged male breast tissue (gynecomastia)
• Decrease in muscle strength and mass
• Decrease in endurance
• Slowed growth in height, with arms and legs growing out of proportion (children)
• Reduced development of pubic hair (children)
• Reduced growth of penis and testicles (children)
• Less voice deepening (children)
• Lower-than-normal strength and endurance (children)

Source: Cleveland Clinic, 2022

When to see a doctor

If you are a young man experiencing multiple symptoms of low testosterone, it is important to consult a healthcare provider. Blood tests can measure testosterone levels, and further investigations can help identify underlying causes. For more convenience, you can also check your hormone levels at home with the Homed-IQ Testosterone Test, which provides accurate results from a simple finger-prick blood sample.

Tips for supporting healthy testosterone levels

Simple lifestyle choices can make a big difference in keeping testosterone levels healthy; here are some key tips:

• Maintain a healthy weight: Excess belly fat lowers testosterone; weight loss can boost levels.
• Exercise: Strength training and cardio both support testosterone, especially heavy compound lifts.
• Eat well: Focus on protein, healthy fats, vegetables, and foods like oysters, onions, fatty fish, and olive oil.
• Sleep 7-9 hours and manage stress
• Limit alcohol: Heavy drinking disrupts hormones; keep it to one drink a day or less.
• Quit smoking: Tobacco harms sperm quality and hormone balance.
• Check medications with your doctor (& treat underlying health issues)

Source: Fisher, J., 2024.

Summary

Testosterone is the key male sex hormone, vital for sexual development, muscle and bone strength, mood, and fertility. In young men, persistently low levels may result from lifestyle factors, medical conditions, or genetics, leading to symptoms like fatigue, reduced libido, and infertility. Diagnosis through blood testing or an at-home testosterone test is important, while healthy habits such as good sleep, exercise, stress reduction, and balanced nutrition help support normal levels.

References

Cleveland Clinic. (2022, September 2). Low testosterone (male hypogonadism). Cleveland Clinic. Retrieved on 21.9.25 from https://my.clevelandclinic.org/health/diseases/15603-low-testosterone-male-hypogonadism

Cleveland Clinic. (2022, October 20). Testosterone: What it is, function & levels. Cleveland Clinic. Retrieved on 21.9.25 from https://my.clevelandclinic.org/health/articles/24101-testosterone

Fisher, J. (2024, August 13). Lifestyle strategies to help prevent natural age-related decline in testosterone. Harvard Health Publishing. Retrieved on 21.9.25 from https://www.health.harvard.edu/mens-health/lifestyle-strategies-to-help-prevent-natural-age-related-decline-in-testosterone

Kafel, H., Braga‐Basaria, M., & Basaria, S. (2025). Opioid‐induced androgen deficiency in men: Prevalence, pathophysiology, and efficacy of testosterone therapy. Andrology.

Leproult, R., & Van Cauter, E. (2011). Effect of 1 week of sleep restriction on testosterone levels in young healthy men. Jama, 305(21), 2173-2174.

Ma, H., Sun, J., Wu, X., Mao, J., & Han, Q. (2024). Percent body fat was negatively correlated with Testosterone levels in male. PLoS One, 19(1), e0294567.

Patel, P., Fantus, R., Lokeshwar*, S., Halpern, J., Chang, C., Kargi, A., & Ramasamy, R. (2020). MP78-01 TRENDS IN SERUM TESTOSTERONE LEVELS AMONG ADOLESCENT AND YOUNG ADULT MEN IN THE UNITED STATES. Journal of Urology, 203(Supplement 4), e1173. https://doi.org/10.1097/JU.0000000000000964.01 (Original work published April 1, 2020)

Pivonello, R., Salzano, C., Galdiero, M., & Colao, A. (2017). Male Hypogonadism Due to Disorders of the Pituitary and Suprasellar Region. In Male Hypogonadism: Basic, Clinical and Therapeutic Principles (pp. 169-186). Cham: Springer International Publishing.

Rodprasert, W., Toppari, J., & Virtanen, H. E. (2021). Endocrine disrupting chemicals and reproductive health in boys and men. Frontiers in endocrinology, 12, 706532.

Shah, S. S., Kanani, E. A. M., Kharat, S. K., Shah, P. S., & Shah, R. M. (2024). Evaluation of the Incidence of Low Testosterone Levels in Young Male Adults with Moderate to Severe Obesity—Single-Centre Study from India. Obesity Surgery, 34(3), 836-840.

Walsh, J. S., Marshall, H., Smith, I. L., Greenfield, D. M., Swain, J., Best, E., … & Ross, R. J. (2019). Testosterone replacement in young male cancer survivors: a 6-month double-blind randomised placebo-controlled trial. PLoS medicine, 16(11), e1002960.

Whittaker, J., & Wu, K. (2021). Low-fat diets and testosterone in men: Systematic review and meta-analysis of intervention studies. The Journal of steroid biochemistry and molecular biology, 210, 105878.

White, J. T., Carto, C., Loloi, J., & Ramasamy, R. (2022). HYPOGONADISM AND TESTOSTERONE THERAPY AMONG MEN WITH KLINEFELTER SYNDROME: ANALYSIS OF A GLOBAL FEDERATED RESEARCH NETWORK. Fertility and Sterility, 118(4), e312.

Xu, P., Choi, E., White, K., & Yafi, F. A. (2021). Low testosterone in male cancer patients and survivors. Sexual medicine reviews, 9(1), 133-142.