When people think of energy, mood, and vitality, they often point to testosterone levels or thyroid health separately. But the reality is far more interconnected. Both the thyroid and testosterone systems act as conductors in the body’s hormonal orchestra, influencing metabolism, strength, sexual health, and even mental clarity. The question many patients ask—can low thyroid cause low testosterone?—isn’t just academic. It has profound implications for men and women struggling with fatigue, weight gain, low libido, and mood issues.

Understanding this relationship matters because thyroid dysfunction and low testosterone often overlap. Men frequently wonder, do men have thyroids? The answer is yes, and thyroid health can shape their testosterone output just as much as women’s estrogen balance. Likewise, women with hypothyroidism may notice lower libido and energy tied to testosterone decline.

In this 2025 guide, we’ll explore how the thyroid and testosterone interact, what symptoms to look for, the science behind hormonal cross-talk, testing strategies, treatment paths, and lifestyle solutions. You’ll also find case studies, myth-busting insights, and actionable steps to take if you’re concerned about your own hormone balance.

By the end, you’ll have a clear answer to can low thyroid cause low testosterone, an understanding of whether low testosterone causes thyroid problems in return, and a roadmap to restoring your energy and vitality through comprehensive endocrine health.

Can Low Thyroid Cause Low Testosterone? The Hormonal Connection

The thyroid gland produces hormones (T3 and T4) that regulate metabolism and influence almost every organ. Testosterone, on the other hand, is produced mainly in the testes, but its regulation depends on signals from the brain’s hypothalamic-pituitary-gonadal (HPG) axis.

When thyroid hormone levels drop, this entire system slows down. Scientific studies show that:

• Hypothyroidism lowers luteinizing hormone (LH) secretion, which is critical for testosterone production.
  
• Reduced thyroid activity decreases sex hormone-binding globulin (SHBG), leading to altered free testosterone levels.
  
• Long-term low thyroid function can impair sperm production and fertility.

Signs That Can Low Thyroid Cause Low Testosterone Issues in Men

One of the most frustrating aspects of male hormonal health is how overlapping the symptoms can be. Both thyroid dysfunction and testosterone deficiency can present with nearly identical signs, making diagnosis tricky without proper testing. This leads many men to wonder: if they feel tired, sluggish, and less motivated, can low thyroid cause low testosterone at the same time?

Some of the most common shared symptoms include:

• Fatigue and low energy despite adequate sleep.
  
• Weight gain or inability to lose weight, especially around the midsection.
  
• Low libido and sexual dysfunction such as erectile issues.
  
• Brain fog with difficulty concentrating and poor memory.
  
• Mood changes including irritability, anxiety, or depression.

Because both conditions produce nearly identical signs, men often end up treated for one while the other remains unrecognized. For example, a man may be given testosterone therapy but still feel tired because an untreated thyroid disorder lingers in the background. Conversely, treating hypothyroidism alone may not fully restore sexual function if testosterone is also low.

Ultimately, recognizing that can low thyroid cause low testosterone is not just possible but common helps patients and doctors look at the bigger hormonal picture rather than chasing isolated symptoms.

Thyroid Function and Male/Female Hormones

What the Thyroid Does (TSH, T3, T4 explained)

The thyroid is a butterfly-shaped gland in your neck that produces hormones critical to energy, metabolism, and overall vitality. Its primary products are thyroxine (T4) and triiodothyronine (T3), which regulate how cells use energy. These hormones are governed by thyroid-stimulating hormone (TSH), secreted by the pituitary gland.

When thyroid levels fall, every system slows down—metabolism, heart rate, digestion, even brain activity. This sluggish state, known as hypothyroidism, doesn’t just cause fatigue and weight gain—it also ripples into sex hormone regulation. Researchers have long studied whether can thyroid problems cause low testosterone, and mounting evidence suggests yes, particularly when thyroid dysfunction alters hormone-binding proteins and pituitary signals.

Testosterone 101 (Roles in Men and Women)

Testosterone isn’t just the “male hormone.” While men produce most of it in the testes and women produce smaller amounts in the ovaries, it’s vital for both sexes. Testosterone influences:

• Libido and sexual health
  
• Muscle mass and strength
  
• Mood stability and energy
  
• Fertility and reproductive function
  

For men, testosterone is central to vitality, but many don’t realize its connection to thyroid health. And in case you’re wondering, do men have thyroids? Yes — every person has a thyroid gland, and in men, thyroid dysfunction can directly affect testosterone production and regulation.

How Endocrine Axes Communicate (HPG & HPT axes)

Hormones don’t work in isolation. The hypothalamic-pituitary-thyroid (HPT) axis regulates thyroid function, while the hypothalamic-pituitary-gonadal (HPG) axis controls testosterone production. These systems share common regulators in the brain and influence each other.

When thyroid function drops, the pituitary often adjusts other signals like luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are essential for testosterone synthesis. This is one mechanism by which can low thyroid cause low testosterone becomes a clinical reality.

Can Low Thyroid Cause Low Testosterone in Men?

Yes, thyroid problems can cause low testosterone in men. Hypothyroidism, hyperthyroidism, and autoimmune thyroid diseases all disrupt hormone regulation. For example:

• Hypothyroidism reduces testosterone production.
  
• Hyperthyroidism increases SHBG, making testosterone less available.
  
• Hashimoto’s disease causes hormonal instability, impacting both thyroid and testosterone.
  

This shows that thyroid health directly impacts male vitality. Early testing and treatment can restore balance.

Direct Mechanisms (what studies suggest)

Scientific studies show that hypothyroidism can lower testosterone through multiple pathways. First, it increases sex hormone–binding globulin (SHBG), which binds testosterone and reduces the “free” form available to tissues. Second, it alters LH and FSH secretion, dampening testicular testosterone production. Third, it can directly disrupt Leydig cell activity in the testes.

Scientific studies show that hypothyroidism can reduce testosterone in several ways:

• SHBG (sex hormone–binding globulin): Low thyroid reduces SHBG, altering how much testosterone is available for use.
  
• LH and FSH signaling: Hypothyroidism disrupts luteinizing hormone and follicle-stimulating hormone, both required for testosterone production.
  
• Testicular function: Prolonged low thyroid may impair direct testicular testosterone synthesis.

This explains why researchers repeatedly affirm: can low thyroid cause low testosterone? Yes, and the connection is not just theoretical. Clinical trials demonstrate that men with hypothyroidism often show significant reductions in testosterone, which improve after thyroid hormone replacement.

Indirect Mechanisms (Inflammation, Metabolic Changes, Obesity)

Beyond direct hormonal disruption, hypothyroidism creates metabolic changes that indirectly suppress testosterone. Low thyroid function promotes weight gain, insulin resistance, and systemic inflammation—all of which blunt testosterone production.

This is another reason can thyroid problems cause low testosterone is a valid concern. Thyroid dysfunction sets off a domino effect that worsens body composition, cardiovascular risk, and sex hormone balance simultaneously.

Population Data: Who’s Most at Risk?

Not everyone with hypothyroidism experiences low testosterone, but certain groups are at higher risk. Older men, individuals with long-standing untreated hypothyroidism, and those with autoimmune thyroiditis (like Hashimoto’s disease) face the greatest overlap.

• Older men (over 50)
  
• Men with autoimmune thyroiditis (Hashimoto’s disease)
  
• Patients with long-standing untreated hypothyroidism
  

These groups show higher overlap between low thyroid and low testosterone, reinforcing the question: can low thyroid cause low testosterone? The answer is yes, particularly in high-risk populations.

Symptoms Overlap: Low Thyroid vs Low Testosterone

The symptoms of hypothyroidism often mimic low testosterone, which makes diagnosis tricky.

Symptoms	Low Thyroid (Hypothyroidism)	Low Testosterone
Fatigue	Yes	Yes
Weight gain	Yes	Yes
Depression & mood changes	Yes	Yes
Low libido	Rare	Yes
Cold intolerance	Yes	No
Muscle weakness	Yes	Yes

Shared Symptoms

Both hypothyroidism and low testosterone can cause similar, frustrating symptoms: 

• Fatigue and low energy
  
• Weight gain and slowed metabolism
  
• Low libido and poor sexual performance
  
• Mood swings, depression, or brain fog
  

This overlap often leads patients to misdiagnose themselves. They may assume testosterone is the problem, when the root issue may be thyroid-related. So, can low thyroid cause low testosterone symptoms? Absolutely.

Distinguishing Symptoms — What’s Unique to Each?

• Thyroid-specific signs: Cold intolerance, constipation, dry skin, brittle hair, swelling in the neck (goiter).
  
• Testosterone-specific signs: Reduced facial hair, decreased muscle strength, smaller testicular size, fewer morning erections.

Understanding these differences helps patients and doctors pinpoint whether the thyroid, testosterone, or both are involved.

Do Men Have Thyroids?

A common misconception is that only women have thyroid issues. But men often ask: Do men have thyroids? The answer is yes. Men also have thyroid glands, and thyroid disorders affect them too. The difference is that thyroid disease is less frequently diagnosed in men because symptoms are often mistaken for aging or stress.

Understanding this helps men in NYC and beyond realize that thyroid testing is just as important as testosterone testing for men’s health.

Diagnosis and Treatment: Addressing Both Conditions Together

Doctors evaluate thyroid and testosterone levels together to rule out overlapping conditions. Testing both avoids misdiagnosis.

Treatment options may include:

• Thyroid hormone replacement therapy (Levothyroxine).
  
• Testosterone replacement therapy (TRT) if levels remain low.
  
• Lifestyle strategies such as weight management, stress reduction, and a nutrient-rich diet.

Treating only one imbalance often fails. For example, giving testosterone without fixing thyroid issues may not restore full vitality.

Diagnosis: Tests to Check Both Thyroid and Testosterone

Thyroid Panel: TSH, Free T4, Free T3, Antibodies

A complete thyroid panel includes:

• TSH (best screening test)
  
• Free T4 (active thyroid hormone)
  
• Free T3 (most metabolically active form)
  
• TPO antibodies (to detect autoimmune thyroid disease)
  

These help determine whether low thyroid is causing low testosterone.

Testosterone Testing: Total vs Free, When to Test

Doctors measure both total testosterone and free testosterone. Testing should be done in the morning when levels peak. If abnormal, repeat testing is needed for confirmation. This is also the point to ask: can low testosterone cause thyroid problems? While less common, there’s evidence of bidirectional influence.

When to Order Advanced Endocrine Workups

If both thyroid and testosterone tests are abnormal, your doctor may order:

• LH and FSH (pituitary signals)
  
• Prolactin (pituitary hormone that can suppress testosterone)
  
• SHBG (affects free testosterone levels)
  
• Thyroid imaging (if nodules are suspected)

Treatment Paths: If Low Thyroid Is Causing Low Testosterone

Treat the Thyroid First: Levothyroxine & Monitoring

In many cases, restoring normal thyroid function with levothyroxine helps normalize testosterone. Several studies show that men with hypothyroidism regain testosterone balance once thyroid hormones are corrected. So, can low thyroid cause low testosterone? Yes — and fixing the thyroid often fixes testosterone.

When Testosterone Therapy Is Considered

If testosterone remains low despite thyroid treatment, doctors may consider TRT (testosterone replacement therapy), clomiphene, or hCG. However, starting TRT without addressing the thyroid first can mask underlying problems. Both thyroid problems can cause low testosterone and, in rare cases, low testosterone can cause thyroid problems.

Combined Management: Multidisciplinary Approach

Optimal care often requires coordination between an endocrinologist, urologist, nutritionist, and sometimes mental health specialists. This ensures that treatment addresses all aspects of hormone balance.

Conclusion

So, can low thyroid cause low testosterone? Absolutely. The thyroid gland and testosterone production are deeply connected. For men in NYC and across the USA, unexplained fatigue, weight gain, or low libido may point to thyroid dysfunction, testosterone deficiency, or both.

A holistic hormonal evaluation is the best way forward. If you suspect thyroid or testosterone issues, consult a specialist. Don’t ignore the signs—restoring balance can dramatically improve quality of life.

Don’t ignore the signs. A holistic approach to endocrine health can restore balance, energy, and vitality. If you suspect low thyroid or testosterone, consult a trusted hormone specialist in New York City at TRTNYC.com.

FAQs

1. Can low thyroid cause low testosterone in young men?

Yes. Even younger men can experience thyroid dysfunction, which may lower testosterone and impact energy, mood, and fertility.

2. Can thyroid problems cause erectile dysfunction?

Yes. Low thyroid can reduce testosterone and blood circulation, contributing to ED.

3. Do men have thyroids like women?

Yes, men have thyroids. They are simply less diagnosed, leading to the misconception it’s a women’s condition.

4. Can low testosterone cause thyroid problems?

In some cases, yes. Testosterone deficiency can indirectly affect thyroid function by altering metabolism and fat distribution.

5. What tests should men request for thyroid and testosterone issues?

TSH, Free T4, Free T3, thyroid antibodies, total testosterone, free testosterone, and SHBG.

6. Can treating hypothyroidism improve testosterone naturally?

Yes. In many cases, correcting low thyroid restores testosterone without TRT.

7. Where can I get tested in NYC?

You can visit hormone specialists or clinics like TRTNYC.com for comprehensive endocrine testing and personalized treatment.