What is Testosterone Replacement Therapy?

If you’ve ever wondered whether feeling constantly tired, low in motivation, or not quite like yourself could be related to hormones, you’re not alone. According to the American Urological Association, low testosterone (aka Low T) impacts roughly 28 percent of men in the United States. Luckily, testosterone replacement therapy can help restore these levels to reduce unwanted symptoms and improve overall quality of life. 

First, What Is Testosterone?

Testosterone is the primary male sex hormone. It plays a major role in:

• Libido and sexual function
• Muscle mass and strength
• Bone density
• Red blood cell production
• Mood and motivation
• Fat distribution

Testosterone levels naturally fluctuate throughout the day (they’re highest in the morning) and gradually decline with age.

What Is Testosterone Replacement Therapy (TRT)?

Testosterone replacement therapy is a medical treatment that provides external testosterone to men whose bodies are not producing enough on their own.

The goal of TRT is simple: To restore testosterone levels into a normal physiological range and relieve symptoms caused by deficiency.

It is important to understand what TRT is not:

• It is not a general “anti-aging” treatment.
• It is not meant to enhance athletic performance.
• It is not recommended for men with normal testosterone levels.

How Do Doctors Diagnose Low Testosterone?

Because testosterone fluctuates, diagnosis requires careful testing. Guidelines recommend:

• Early morning blood draws (typically before 10 a.m.)
• At least two separate measurements
• Consistently low total testosterone levels (often below ~300 ng/dL, depending on lab reference ranges)

If levels are borderline or if certain binding proteins are abnormal, doctors may also evaluate free testosterone.

Just as important, clinicians often check additional labs (LH, FSH, prolactin) to determine whether the issue originates in the testes (primary hypogonadism) or in the brain’s signaling system (secondary hypogonadism).

In other words, good medicine here means more than just ordering one quick lab.

What Symptoms Might Point Toward Testosterone Deficiency?

Low testosterone symptoms can include:

• Reduced libido
• Erectile dysfunction
• Fatigue
• Loss of muscle mass
• Increased body fat
• Low mood
• Decreased bone density
• Unexplained anemia

But here’s the important part: These symptoms are not specific to low testosterone.

Sleep deprivation, depression, thyroid disorders, obesity, diabetes, medications (like opioids), and chronic stress can all produce similar complaints. That’s why responsible evaluation is so critical.

How Does TRT Work?

When testosterone is administered (through injections, gels, patches, or pellets) it enters the bloodstream and binds to receptors throughout the body. This activates gene expression that influences muscle, bone, red blood cells, libido, and more.

However, TRT also suppresses the body’s natural testosterone production. According to the ‘Endocrine Society Clinical Practice Guideline: Testosterone Therapy in Men with Hypogonadism’, External testosterone signals the brain to reduce luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which decreases testicular testosterone and sperm production.

That’s why TRT can significantly impact fertility—a crucial discussion for younger men.

What Are the Proven Benefits of TRT?

When prescribed appropriately for confirmed hypogonadism, TRT has demonstrated several evidence-supported benefits.

1. Improved Sexual Function

Large randomized trials, including the Testosterone Trials published in the New England Journal of Medicine, showed improvements in sexual desire and sexual activity in older men with low testosterone.

2. Increased Lean Body Mass

A meta-analysis published in the Journal of Clinical Endocrinology & Metabolism shows that TRT increases lean body mass and reduces fat mass in hypogonadal men.

3. Improved Bone Density

Testosterone therapy has been shown to increase bone mineral density, which may help reduce fracture risk over time (Snyder et al., NEJM, 2017).

4. Correction of Anemia

The Testosterone Trials also found that TRT improved unexplained anemia in older men with low testosterone.

5. Mood and Energy (With Nuance)

In a 2019 study published in JAMA Psychiatry, researchers found modest improvements in mood and depressive symptoms, particularly in men with clear biochemical deficiency. 

What Are the Risks?

Like any hormone therapy, TRT is not risk-free.

1. Elevated Hematocrit (Thicker Blood)

Testosterone stimulates red blood cell production. In some men, this can lead to erythrocytosis, which may increase clot risk. Regular blood monitoring is required.

2. Fertility Suppression

TRT can significantly reduce sperm production. Men wishing to conceive should discuss alternatives with a specialist.

3. Cardiovascular Considerations

Cardiovascular risk has been debated. Earlier observational studies suggested possible risk, but more recent large randomized trials, including the TRAVERSE trial, did not demonstrate increased major adverse cardiovascular events in appropriately selected men. However, blood pressure monitoring remains important.

4. Other Possible Effects

• Acne
• Fluid retention
• Breast tenderness
• Worsening untreated sleep apnea

Monitoring helps manage these risks.

How Is TRT Given?

Common delivery methods include:

• Intramuscular or subcutaneous injections
• Topical gels
• Transdermal patches
• Implanted pellets

Each method has pros and cons related to cost, convenience, hormone stability, and side effects. The goal is to maintain testosterone in a mid-normal physiological range—not supraphysiologic levels.

Who Should Not Take TRT?

TRT is generally avoided in men who:

• Are actively trying to conceive
• Have prostate or breast cancer
• Have untreated severe sleep apnea
• Have uncontrolled heart failure
• Have significantly elevated hematocrit

Again, careful screening is key.

Do You Have Questions About Whether TRT is Right for You?

Our Santa Rosa, CA-based clinic offers discreet, men’s health care from our award-winning naturopathic medical doctors. If you’re local to our area or live anywhere in California, we offer experienced, virtual, and in-person care for your sexual health needs.