Testosterone is an important male sex hormone that is crucial to overall health and well-being. It promotes strength, muscle mass, bone density, sex drive, energy levels, and more in men. Testosterone production reaches its peak in early adulthood and gradually declines with age. Low testosterone, also known as low T or hypogonadism, has become increasingly common among middle-aged and older men.

It is estimated that 2-4 million men in the United States have consistently low testosterone levels. The prevalence increases with age – some studies suggest that over 50% of men over 80 may have deficient levels. As the population ages, low T is expected to become even more widespread.

The symptoms of low testosterone can significantly impact quality of life. They include low libido, erectile dysfunction, fatigue, loss of muscle mass, increased body fat, reduced bone density, irritability, and depression. While some amount of decline in testosterone is normal with aging, more severe or premature deficiency warrants medical evaluation and treatment.

If low testosterone goes untreated, it can lead to loss of independence, increased risk of falls and fractures, diabetes, cardiovascular disease, and other complications. Therefore, it is important for aging men to be aware of the signs and risk factors of low T. Diagnosing and properly managing low testosterone can help restore strength, energy, sexual function, and overall health.

What are the Main Causes of Low Testosterone?

There are several potential causes of low testosterone in men:

  • Aging and natural decline
  • Medical conditions
  • Injuries or surgery
  • Medications
  • Genetic conditions
  • Unhealthy lifestyle
  • Autoimmune disorders

– Testosterone levels peak in early adulthood and drop about 1% per year after age 30. One large study found that 39% of men over age 45 had symptomatic low testosterone. [1]
– Chronic conditions like obesity, type 2 diabetes, metabolic syndrome, HIV/AIDs, COPD, end-stage kidney disease, cirrhosis, and pituitary disorders can impair testosterone production. [2][3]
– Trauma to the testes from injury, chemotherapy, radiation, or surgery for testicular cancer can damage Leydig cells that produce testosterone. [4]
– Long-term use of corticosteroids, opioids, anticonvulsants, 5-alpha reductase inhibitors, and some antidepressants may impact testosterone levels. [5]
– Rare disorders like Klinefelter syndrome, Kallmann syndrome, and Kennedy disease are associated with abnormally low testosterone. [6]
– Factors like inadequate sleep, excessive alcohol, drug abuse, chronic stress, and malnutrition contribute to low T. [7]
– In some cases, the body may develop antibodies against its own testosterone. [8]
[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190174/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4691179/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5508412/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1472884/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6431559/
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5795588/
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1472884/

As men age, testosterone levels begin to decline after age 30, T levels dropping 1-2% per year. This slow, gradual decline in testosterone is sometimes referred to as late-onset hypogonadism or andropause. It results from changes in hormones as well as testicular tissue and function.

Medical Conditions

Several medical conditions are associated with lower testosterone levels. Chronic conditions like obesity, type 2 diabetes, metabolic syndrome, HIV/AIDs, liver or kidney disease, pituitary disorders, sleep apnea may lower testosterone production.

Injuries and Surgery

Physical trauma to the testicles from injury, cancer surgery, or chemotherapy can damage the Leydig cells responsible for testosterone synthesis. Brain surgery involving the hypothalamus or pituitary can impair hormone balance and testosterone secretion.


Various prescription drugs influence testosterone levels. Long-term use of corticosteroids, opioids, anti-fungals, 5-alpha reductase inhibitors, and some antidepressants may impact testosterone levels.

Genetic Conditions

Certain genetic disorders present at birth result in low testosterone. Rare disorders like Klinefelter syndrome, Kallmann syndrome, and Kennedy disease are associated with abnormally low testosterone.

Unhealthy lifestyle

Stress, poor diet, lack of sleep, excessive alcohol use, and anabolic steroid withdrawal may temporarily reduce testosterone as well. Identifying and addressing the underlying causes is key to improving T levels long-term.


Signs and Symptoms of Low T in Men

The most common and prominent symptom of low testosterone in men is low sex drive or reduced libido. Men with declining testosterone levels often notice a decrease in sexual desire and fewer spontaneous erections. Where they previously had a regular interest in sex, they now experience a lack of motivation and need for sexual activity. Loss of sex drive is often one of the first noticeable symptoms as testosterone levels decline.

Other symptoms such as erectile dysfunction, fatigue, mood changes, and muscle loss tend to develop more gradually. However, the severity and rate at which symptoms progress varies considerably among men with low testosterone. Some men with minor decreases in testosterone may not have noticeable symptoms, while others with very low levels can be profoundly impacted.

The feeling of low testosterone symptoms depends on how low levels are, individual sensitivity, and age

Reduced Libido

Low testosterone often manifests as a decrease in libido or sex drive. Men may experience fewer spontaneous erections, have less motivation for sex, and reduced sexual fantasizing [1]. Loss of morning erections is another indicator of low T as this corresponds with natural peaks in testosterone levels [2].

Erectile Dysfunction

Difficulty achieving or maintaining firm erections sufficient for sexual activity is a common symptom of low T. The causes are multifactorial but low T contributes by reducing nitric oxide availability and penile blood flow [3].


Excessive tiredness, lack of energy, and diminished endurance are frequently reported in men with low T. Simple physical tasks become noticeably more difficult. This correlates with reductions in hemoglobin, muscle mass, and oxygen uptake that accompany testosterone deficiency [4].

Depressed Mood

Irritability, mood swings, and depression are observed in men with chronically low testosterone. There appears to be a bidirectional relationship between low T and depression via interacting physiological mechanisms [5]. Treatment of low testosterone may improve depressive symptoms.

Reduced Muscle Mass

Declines in lean muscle mass and upper and lower body strength result from low T. Testosterone plays a vital role in muscle protein synthesis. Reduced muscle mass can lead to weight gain and reduced mobility [6].

Increased Body Fat

Low testosterone is linked with increased body fat, especially abdominal or visceral fat. Loss of muscle along with hormonal changes due to low T promote fat accumulation [7].

Cognitive Difficulties

Impairments in memory, concentration, focus, and verbal fluency may occur. Though reversible, prolonged low T can lead to structural brain changes [8].

Sleep Disturbances

Low T appears to disrupt sleep patterns and quality. Men may experience insomnia, frequent awakenings, and less deep sleep. In turn, poor sleep exacerbates low T [9].

Hot Flashes and Sweating

Vasomotor symptoms like hot flashes, sweating, and flushing can occur akin to perimenopausal women. The mechanism involves a complicated relationship between sex hormones and the hypothalamus [10].


Low free testosterone relative to estradiol sometimes causes gynecomastia or enlarged male breast tissue and sensitivity. This is reversible once hormone levels normalize [11].

Low Semen Volume

Testosterone stimulates spermatogenesis along with follicle stimulating hormone (FSH). Low T can hence lead to reduced semen volume and sperm production [12].

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6087849/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/
[3] https://www.urologyhealth.org/healthy-living/urologic-conditions/low-testosterone/treatment
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709428/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5356980/
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190174/
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3955331/
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329652/
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5702623/
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/
[12] https://www.urologyhealth.org/healthy-living/urologic-conditions/low-testosterone


Evaluating low testosterone requires a combination of clinical evaluation along with blood tests to check total testosterone, free testosterone, and other hormone levels.

Medical History

The physician will ask about symptoms, medical conditions, medications, injuries, and family history to help determine potential causes of low T. Information on lifestyle factors like diet, exercise, sleep, stress, and alcohol use is also gathered.

Physical Exam

A physical exam looks for signs related to low testosterone like reduced body hair, gynecomastia, small testicle size, and altered fat distribution. A genital exam evaluates the penis and testes. Prostate exam screens for enlargement suggestive of cancer.

Blood Tests

Total testosterone level is tested, ideally in the early morning when levels peak. Levels below 300 ng/dL are considered low [1]. Free testosterone, the hormone not bound to proteins, is also tested as it reflects bioavailable levels.

Other relevant labs may include:

  • Complete blood count to check for anemia
  • Thyroid panel to assess for hypothyroidism
  • Prolactin to check for pituitary tumors
  • Estradiol to assess for aromatization

Follow-up tests may be ordered to pinpoint underlying causes such as genetic testing, MRI of the pituitary, or biopsy for testicular failure.

Normal total testosterone levels generally range from 300-1000 ng/dL. Optimal levels for most men fall between 500-700 ng/dL [2]. Free testosterone levels above 130 pg/mL are considered normal [3].

Symptoms and lab results are considered together in diagnosing low T since men can still have symptoms at “normal” levels, especially as they age.

[1] https://urology.ucsf.edu/patient-care/men%E2%80%99s-health-male-infertility/low-testosterone
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190174/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/


Treatment of low testosterone focuses on replacing testosterone to normal levels and addressing any underlying conditions contributing to deficiency. There are several options for testosterone replacement therapy (TRT):

  • Intramuscular injections – Testosterone injections every 1-2 weeks are commonly used. Levels rise into the supraphysiologic range initially after injections and decline prior to the next dose.
  • Transdermal patches – Adhesive testosterone patches worn on the skin allow absorption. Patches must be replaced daily or twice daily. Skin reactions may occur.
  • Gels – Topical testosterone gels/solutions are spread daily onto the arms, shoulders or abdomen. Testosterone transfers through the skin into the bloodstream. Transfer to others through skin contact is a potential concern.
  • Pellets – Testosterone pellets implanted under the skin every 3-6 months provide sustained release of hormone. Minor surgery is required for placement and removal.
  • Oral tablets – Unmodified oral testosterone is ineffective due to extensive first-pass liver metabolism. Modified forms like testosterone undecanoate provide some benefits but have limitations.

Monitoring and follow-up tests are conducted to keep levels in the ideal range while avoiding major side effects. Testosterone levels are typically rechecked 1-3 months after initiating therapy and regularly thereafter to ensure the dose is optimized. The goal is to maintain testosterone levels in the mid-normal physiologic range, around 500-700 ng/dL for most men [1].

Higher doses that elevate testosterone above the normal range provide no additional benefit and increase the risks of side effects like polycythemia, sleep apnea, prostate enlargement, heart disease, and fluid retention [2]. At the same time, low or inadequate dosing fails to relieve the symptoms of deficiency. Therefore, ongoing monitoring and dose adjustments are important.

It is also important to note that testosterone replacement therapy does not permanently restore the body’s natural testosterone production. Exogenous testosterone administration signals the testes to shut down remaining natural production via a negative feedback loop [3]. If TRT is discontinued, this will result in an accelerated decline in testosterone levels. Some doctors prescribe human chorionic gonadotropin (hCG) to help maintain testicular function along with TRT. However, most men do require lifelong treatment to maintain testosterone levels.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4190174/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1476085/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4854084/

Risks and Complications of Not Treating Low T

While testosterone treatment does carry some risks if not properly managed, untreated testosterone deficiency can lead to several adverse effects on men’s health:

  • Bone loss – Low T is associated with accelerated bone loss, osteopenia, and increased fracture risk. Testosterone promotes bone mineral density by stimulating osteoblasts [1].
  • Declining muscle mass and strength. from low T results in loss of physical function. This frailty increases the risk of falls, disability, loss of independence, and death [2].
  • Cardiovascular disease – Low testosterone correlates with a higher rate of cardiovascular events. It contributes to metabolic syndrome, diabetes, obesity, and atherosclerosis [3].
  • Cognitive impairment – Long term low T leads to structural brain changes including reduced hippocampus volume. Verbal memory in particular appears affected [4].
  • Depression – The mood effects of low T may progress to major depression in some men. Risk of suicide is increased if depression is left untreated [5].
  • Anemia – Testosterone boosts red blood cell production. Deficiency can thus contribute to anemia and related fatigue [6].
  • Metabolic effects – Low T promotes loss of insulin sensitivity and is associated with higher all-cause mortality in diabetic men [7].
  • Cognitive impairment – Prolonged low T may accelerate cognitive decline and neurodegenerative diseases like Alzheimer’s [5].
  • Increased mortality – Studies associate untreated low T with higher all-cause mortality and cardiovascular death [6]. TRT could decrease mortality by 10-20% [7].

Careful consideration of benefits and risks is important when determining whether to treat low T. However, foregoing treatment also comes with substantive risks related to the hormone deficiency itself. Lifestyle measures, screening for underlying conditions, and possibly TRT under medical supervision may help mitigate the complications of low testosterone.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4335450/
[2] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709428/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3891203/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4329652/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5356980/
[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709428/
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3891203/