The hidden epidemic: Why thyroid disorders often go undiagnosed

Your thyroid–a small, butterfly-shaped gland at the base of your neck–has influence far beyond its size. This powerhouse gland controls your metabolism, energy production, heart rate, digestion, brain function, and even mood stability. Every single cell in your body relies on thyroid hormones to function properly.

When your thyroid is out of balance, every system in your body feels the impact. But symptoms can be vague or mimic other conditions, making thyroid dysfunction often go undiagnosed.

• 1 in 8 women will develop a thyroid disorder in their lifetime, making them up to eight times more likely than men to experience thyroid dysfunction.
• Over 50% of thyroid disorders go undiagnosed, meaning millions of people live with symptoms that could be treated.
• Thyroid dysfunction doesn’t just affect energy and weight—it’s linked to heart disease, infertility, depression, and even cognitive decline if left untreated.

With such a profound impact on your health, understand the signs and solutions for thyroid dysfunction to stay in control.

Symptoms

Hypothyroidism symptoms

When your thyroid is underactive and, in turn, doesn’t produce enough hormones, your body’s processes slow down. For women, hypothyroidism is much more common–affecting 1 in 8 during their lifetime. Low thyroid symptoms include:

• Fatigue (even after a full night’s sleep)
• Weight gain (despite no changes in diet or exercise)
• Low sex drive
• Brain fog
• Difficulty concentrating
• Depression or mood swings
• Dry skin and brittle nails
• Hair thinning or loss

Hyperthyroidism symptoms

When your thyroid is overactive, it produces too many hormones. And your metabolism speeds up. Sounds like a good thing, but in reality it can mean:

• Restlessness and nervousness
• Unexplained weight loss
• Irritability and mood swings
• Anxiety
• Sleep disturbances
• Joint pain

Left unchecked, an overactive thyroid can increase your risk of osteoporosis, heart disease, and muscle weakness.

Causes

Thyroid issues don’t happen randomly. They’re often triggered by a mix of nutritional deficiencies, stress, autoimmune conditions, and hormonal shifts. Despite its critical role in metabolism, mood regulation, and overall health, the thyroid is highly sensitive to both external and internal stressors. 

From the food you eat to the medications you take, many factors can either support or sabotage your thyroid health. Understanding these underlying causes can help you take proactive steps to protect and optimize thyroid function before symptoms spiral out of control.

1. Nutrient deficiencies

Iodine*

It’s a key element for thyroid hormone production. Either deficiency or excess of iodine can cause thyroid dysfunction.

Selenium*

This powerful antioxidant supports thyroid hormone conversion, immune health, and cellular protection from oxidative stress by reducing inflammation.

Zinc

Zinc is mostly known for its immune support, but it's actually a powerful mineral across all systems of the body. As it relates to your thyroid, it helps regulate TSH levels and supports thyroid hormone production.

* This lab test is available as an optional enhancement to the annual Function membership.

2. Chronic stress

Your thyroid and cortisol are deeply interconnected. When you're under prolonged stress, your body releases high levels of cortisol–the primary stress hormone. While cortisol is normal and essential in small, regulated amounts, chronically elevated levels will disrupt thyroid function in more ways than one.

Suppresses thyroid-stimulating hormone (TSH)

Chronic stress, associated with high cortisol levels can inhibit the hypothalamic-pituitary-thyroid (HPT) axis, leading to lower TSH production.

Inhibits the conversion of T4 to T3

The thyroid primarily produces thyroxine (T4), an inactive hormone that needs to be converted into triiodothyronine (T3)–the active form that drives metabolism, brain function, and energy. High cortisol blocks this conversion, leading to low T3 levels, even when TSH appears normal. This can cause symptoms of hypothyroidism, with symptoms of fatigue, brain fog, and depression, even if standard thyroid tests don't detect an issue.

Increases reverse T3 (rT3)

Chronic stress can lead to an increase in reverse T3 (rT3), a form of T3 that doesn’t activate thyroid receptors. Essentially, rT3 competes with active T3 but has no functional benefit, further slowing your metabolism and contributing to fatigue and/or weight gain.

Because stress has such a profound impact on thyroid function, stress management is just as important as diet or medication for maintaining thyroid health.

3. Autoimmune conditions

Your immune system is designed to protect you from infections and foreign invaders. However, in some cases, it mistakenly identifies your thyroid as a threat and begins attacking it—leading to autoimmune thyroid disease. The two most common being:

Hashimoto’s thyroiditis (Hypothyroidism)

In this condition, the immune system gradually destroys the thyroid gland, leading to reduced hormone production. Hashimoto’s is the leading cause of hypothyroidism and is far more common in women than men. Symptoms include fatigue, weight gain, depression, cold intolerance, and hair thinning.

Graves’ disease (Hyperthyroidism)

The immune system triggers excess thyroid hormone production, pushing the body into overdrive. People with Graves' disease may experience unexplained weight loss, anxiety, heart palpitations, and sleep disturbances.

These disorders can develop slowly–often going undiagnosed for years. Standard thyroid tests like TSH and T4 may not be enough to detect them. That’s why comprehensive thyroid and whole-body testing is key to understanding what’s really going on inside of your body.

4. Hormonal changes in women

All your hormones are intricately connected. Estrogen, progesterone, and thyroid hormones interact in complex ways. This means that major hormonal shifts—during pregnancy, postpartum, menopause, or while taking birth control—can significantly impact your thyroid function.

During pregnancy & postpartum

While pregnant, your body demands more thyroid hormones to support fetal development. As a result, some women experience a TSH rise in pregnancy, which may signal the onset of hypothyroidism. If left untreated, this can increase your risk of miscarriage, preterm birth, preeclampsia, and developmental delays in your baby.

Postpartum thyroiditis is another concern. Around 5-10% of women develop postpartum thyroid dysfunction, which can start with temporary hyperthyroidism, followed by a period of hypothyroidism as your thyroid slows down. This can cause fatigue, depression, brain fog, and weight changes—symptoms often dismissed as “normal” postpartum.

During menopause

Menopause, associated with a drop in estrogen levels, can alter thyroid function by changing hormone metabolism and immune balance, often leading to shifts in TSH, free T4, and free T3 levels that may mimic or mask thyroid disorders. As menopause and hypothyroidism share overlapping symptoms—such as fatigue, weight gain, mood changes, and brain fog—it is important to use comprehensive lab testing to distinguish between the two. 

As women enter menopause, the shift in hormone levels—especially the drop in estrogen—can trigger a cascade of changes in the body. One area that’s often overlooked? Gut health and nutrient absorption. Estrogen plays a key role in maintaining a healthy gut environment. When levels decline, it can affect everything from digestion to how well you absorb nutrients. That means your body may have a harder time getting the essential vitamins and minerals it needs—including the ones that keep your thyroid running smoothly.

On hormonal birth control

Hormonal birth control works by altering estrogen levels, which can impact thyroid hormone metabolism. Estrogen increases levels of thyroid-binding globulin (TBG), a protein that binds thyroid hormones–and reduces their availability. This means some women may have lower levels of active thyroid hormones while taking hormonal birth control. In turn, leading to symptoms of fatigue and sluggishness.

For women with existing thyroid issues, it’s even more important to monitor thyroid function while using hormonal contraceptives.

Because the thyroid is so sensitive to hormonal changes, women need to be proactive about thyroid testing during every stage: pregnancy, postpartum, perimenopause, and while taking hormonal birth control.

Standard thyroid testing falls short

During an annual physical, typically only Thyroid-Stimulating Hormone (TSH) is checked. While TSH is important, it can’t give you a full picture of your thyroid health. A “normal” TSH level can still mean a thyroid issue is lurking undetected.

To truly understand your thyroid function, comprehensive lab testing is key.

Lab tests

Thyroid-stimulating hormone (TSH)

Hypothyroidism affects about 1 in 8 women and roughly 3% of men in the U.S., making it a common but often overlooked condition. One of the most important tools for detecting thyroid issues is the TSH (thyroid-stimulating hormone) test.

TSH is made by your pituitary gland and tells your thyroid when to release hormones like T3 (triiodothyronine) and T4 (thyroxine). When TSH levels are too high or too low, it can signal that your thyroid is out of balance.

But TSH alone doesn’t tell the full story. To get a clear picture of your thyroid health, it’s important to look at TSH alongside other thyroid labs. Together, these tests help uncover the root of thyroid dysfunction and guide proper treatment.

Triiodothyronine (T3) Free

T3 levels can reveal an overactive (hyperthyroidism) or underactive (hypothyroidism or Hashimoto’s) thyroid. T3 is the most powerful thyroid hormone in the body. It helps regulate body temperature, control heart rate, lower cholesterol, improve memory, promote regrowth after hair loss, soothe muscle aches, regulate bowel movements, and support fertility. However, free T3 doesn’t work in isolation. It’s part of a complex hormone feedback loop that includes TSH (thyroid-stimulating hormone) and free T4 (thyroxine). Evaluating all three gives a more complete understanding of thyroid function and how well the body is activating its hormones at the cellular level.

Thyroxine (T4) Free

This lab test is typically cross-referenced with TSH and T3 to gain insight into overall thyroid function. Thyroxine, or T4, is produced in the thyroid then released into the bloodstream where it travels to the liver and kidneys. It is converted into the active hormone triiodothyronine (T3). The synergy of T4 and T3 is important for heart and digestive function, metabolism, brain development, bone health, and muscle control.

Thyroid Peroxidase (TPO) antibodies

Thyroid peroxidase antibodies (TPO) target thyroid enzymes and are associated with autoimmune thyroid conditions, such as Hashimoto's thyroiditis.

Thyroglobulin antibodies (TgAb)

This test checks for antibodies created against thyroglobulin, a protein produced and used by the thyroid gland to make T3 and T4 hormones, which control metabolism and tissue/cell growth. If present, it may indicate thyroid-related autoimmune disorders, such as Hashimoto’s.

More biomarkers to track

Alongside iodine, selenium, zinc, and thyroid biomarkers, additional lab tests help to provide a whole-body view of your health. Test and track these biomarkers for deeper insights into your thyroid health, nutrient status, and overall metabolic function.

Vitamin D

Vitamin D deficiency is also widely underdiagnosed and undertreated. Low levels have been linked to autoimmune thyroid disorders. The role of vitamin D is vast, and supports your immune system and reduces inflammation in the thyroid, specifically.

Cortisol

Often referred to as “the stress hormone,” cortisol can suppress thyroid function by impairing the conversion of T4 to T3. However, it goes beyond stress to help the body with numerous functions. 

Ferritin

Ferritin is a protein that stores iron in cells and then releases the iron when the body makes more red blood cells. Low ferritin (iron storage) impairs conversion of T4 to T3, while contributing to hair loss–a common symptom of hypothyroidism. Ferritin levels can help diagnose iron deficiency, liver disease, inflammation, or insulin resistance, as well.

hs-CRP

High-sensitivity C-reactive protein (hs-CRP) is an inflammatory marker. Elevated levels indicate chronic inflammation, which can drive autoimmune thyroid disease and metabolic dysfunction. Chronic inflammation is linked to every major disease: heart disease (even before symptoms occur), type 2 diabetes, cancer, high blood pressure, Alzheimer’s, depression, all autoimmune diseases, and severe allergic reactions like asthma.

Role in mental health

Thyroid dysfunction is often misdiagnosed as depression, anxiety, or even bipolar disorder. The relation between thyroid function and depression has long been recognized. Individuals with thyroid disorders are more prone to develop depressive symptoms and conversely depression may be accompanied by various subtle thyroid abnormalities. Traditionally, the most commonly documented abnormalities are elevated T4 levels, low T3, a blunted TSH response, and positive antithyroid antibodies.

If you’ve struggled with mental health issues and standard treatments haven’t worked, it’s worth digging into your thyroid health. For more information on mental health and stress management, visit Mental Health 101 and Stress Management 101.

Solutions

1. Track your symptoms: Don’t ignore unexplained fatigue, weight changes, or mood shifts.
2. Get comprehensive testing: Dig deeper–go beyond just TSH to get a whole-body view of your health.
3. Manage your stress: Chronic stress disrupts thyroid function. Consider movement, meditation, breathing exercises, quality sleep, time in nature, and other tools that work best for you.
4. Optimize nutrition: Be mindful of your intake of:
   
   • Iodine - in seaweed, fish, and iodized salt.
   • Selenium - in Brazil nuts, sunflower seeds, and sardines.
   • Zinc - in oysters, grass-fed beef, chickpeas, and pumpkin seeds.
5. Consider medication: With the right health data, talk to your health provider about what medication or supplementation might be right for you. 

Takeaway

Your thyroid is your body’s metabolic thermostat—when it’s off, everything feels out of sync. If you suspect a thyroid issue, don’t settle for vague explanations like “you’re just getting older” or “it’s probably stress.” You deserve real answers that data can provide.

Take control of your health. Advocate for the right tests. And, most importantly, listen to what your body is telling you.

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