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Low Testosterone

Picture of Dr Afraz Adam

Dr Afraz Adam

Chief Medical Officer
MBBS. FRNZCUC

Low testosterone occurs when the body doesn’t produce enough of this key hormone, leading to low energy, mood changes, reduced sex drive, and fatigue.

Overview
Symptons
Causes
Risk Factors
Diagnosis
Treatment
Prevention

Overview

Understanding Low Testosterone

Testosterone is the main male sex hormone. It drives everything from energy and strength to sex drive and fertility. In New Zealand, as in many countries, testosterone deficiency is common, especially as men get older. Research suggests that up to 40 percent of men over 45 may have low testosterone, and the trend appears to be similar here.

But testosterone deficiency doesn’t just affect older men. Lifestyle factors, weight, stress, and underlying health conditions mean younger men are increasingly being diagnosed too.

Types of Testosterone Deficiency

There are two main types:

  • Primary hypogonadism (testicular failure): This is when the testicles themselves can’t make enough testosterone. Causes include genetic conditions (like Klinefelter’s syndrome), injury, infections such as mumps, or damage from chemotherapy and radiation.
 
  • Secondary hypogonadism: Here, the brain (specifically the hypothalamus and pituitary gland) doesn’t send the right hormonal signals to the testicles. Obesity, pituitary dysfunction, sleep disorders, or certain medications are often involved.
 

Why Testosterone Matters

Testosterone isn’t just about sex. It affects almost every system in the body:

  • Shapes the male reproductive organs before birth
 
  • Triggers puberty: deeper voice, body and facial hair, bigger muscles, stronger bones
 
  • Supports erections, sex drive, and sperm production
 
  • Helps regulate red blood cells, fat distribution, muscle strength, and bone density
 
  • Plays a role in mood, memory, and overall vitality
 

Most testosterone (about 95 percent) is produced in the testicles, but it relies on hormonal signals from the brain to keep production steady. If that system breaks down, testosterone levels fall, and symptoms show up quickly.

What Are Normal Testosterone Levels?

Testosterone levels naturally fluctuate, peaking in the morning and dropping during the day. They also decline gradually with age.

Traditionally, the “normal” range has been defined as 300–1,000 ng/dL. But newer research suggests that younger men should sit higher than this, and that “normal” varies by age group.

Importantly: testosterone deficiency isn’t diagnosed on numbers alone. It’s only considered low when blood test results match up with symptoms.

Symptoms

Signs and Symptoms of Low Testosterone

Low testosterone can show up in different ways depending on age, lifestyle, and health.

Common symptoms include:

  • Erectile dysfunction (weaker erections, fewer morning erections)

  • Trouble sleeping or poor sleep quality

  • Hot flushes or night sweats

  • Smaller testicle size

  • Mood swings, irritability, or low mood

  • Less body or facial hair

  • Breast tissue development (gynecomastia)

  • Trouble sleeping or poor sleep quality

  • Hot flushes or night sweats

  • Memory issues or brain fog

  • Thinning bones (osteoporosis or fractures)

  • Constant tiredness or fatigue

You don’t need to have every symptom on this list, even a few combined with low blood test results may point to testosterone deficiency.

Causes

Causes of Low Testosterone

Low testosterone can be triggered by many factors. Causes usually fall into two groups:

Primary (testicular causes):

  • Klinefelter’s syndrome (genetic condition)

  • Undescended testicles from birth

  • Testicular injury or trauma

  • Past infections (like mumps orchitis)

  • Damage from chemotherapy or radiation

Secondary (brain/pituitary causes):

  • Pituitary or hypothalamus disorders (tumours, surgery, genetic conditions)

  • Obesity and metabolic syndrome

  • Excessive alcohol or drug use (especially opioids or anabolic steroids)

  • HIV/AIDS

  • Natural age-related decline

Risk factors

Risk Factors for Low Testosterone

You may be more likely to develop testosterone deficiency if you have:

  • Age over 40

  • Obesity or type 2 diabetes

  • HIV/AIDS

  • A history of chemotherapy or radiation

  • Chronic opioid use

  • Past or current anabolic steroid use

  • Poor diet or chronic illness

Diagnosis

Diagnosis of Low Testosterone

Testing is simple. Your healthcare provider will:

  • Ask about symptoms and health history

  • Order a morning blood test to check testosterone

  • Sometimes measure related hormones (LH and FSH) to see if the issue starts in the testicles or brain

  • Order blood tests (testosterone, cholesterol, blood sugar, thyroid, kidney/liver function)

Generally, testosterone levels below 300 ng/dL, combined with symptoms, point to testosterone deficiency.

Treatment

Treatment for Low Testosterone

The most common treatment is testosterone replacement therapy (TRT), delivered through gels, patches, injections, or implants. TRT can boost energy, sex drive, mood, and muscle strength while supporting healthy erections.

Other options include:

  • Medications that stimulate natural testosterone production (like clomiphene or hCG)

  • ED medications (Viagra, Cialis, etc.) if erections are affected

  • Lifestyle changes – losing weight, exercising, improving sleep, and reducing stress

TRT isn’t suitable for everyone. It can reduce fertility and may worsen certain conditions like prostate problems or sleep apnoea. That’s why proper testing and medical supervision are essential.

Prevention

Prevention and Support

Not every case of low testosterone can be avoided, but healthy habits help maintain your levels:

  • Stay active and build muscle with regular exercise

  • Keep weight in a healthy range

  • Prioritise good sleep (7–9 hours)

  • Manage stress through relaxation, mindfulness, or therapy

  • Eat a balanced diet rich in protein, healthy fats, and key vitamins

  • Limit alcohol and avoid smoking or drug use