Do I Have a Thyroid Problem?

Recognizing Thyroid Issues: More Than Just Fatigue

Constant fatigue, cold hands, sluggishness, dry skin, unexpected weight gain… Sound familiar? You might wonder if these are signs of menopause, or maybe you’re way too young for that. Surprisingly, the answer might lie in your thyroid.

Your Thyroid: The Body’s Energy Factory

Your thyroid may be small—just a butterfly-shaped organ at the base of your neck—but it plays a tremendous role in keeping your body in harmony.

Imagine your body as a bustling city where every part needs energy to function. At the center sits the Thyroid Factory, producing essential cargo called T3 and T4 thyroid hormones. Once these hormones are ready, they travel through your bloodstream to every tissue, regulating vital functions like heart rate, digestion, and brain activity. When communication breaks down in this assembly line, T3 and T4 production slows—and so do your body’s functions.

Recognizing Hypothyroidism Symptoms

When your thyroid slows down and produces fewer hormones than your body needs, everything else slows down too, leading to what’s often called a “slowed metabolism.” You might experience (1):

• Persistent fatigue: Even small tasks feel exhausting
• Weight gain: Metabolism slows, causing weight to creep up despite no lifestyle changes
• Cold intolerance: Feeling cold even in warm environments
• Dry skin and brittle hair: Reduced cell renewal leads to skin and hair issues
• Constipation: Slower digestion causes bowel changes
• Muscle and joint pain: Reduced muscle strength and repair
• Mood changes: Depression, low motivation, and brain fog
• Anemia: Fewer red blood cells leading to increased fatigue

These are all signs of hypothyroidism—“hypo” means “low,” so hypothyroidism simply means “low thyroid hormones.”

Understanding Your Thyroid Lab Tests

When thyroid problems are suspected, your doctor may order a thyroid function panel including:

• Free Thyroxine (FT4)
• Free Triiodothyronine (FT3)
• Thyroid Stimulating Hormone (TSH)
• Thyroglobulin Antibodies (Anti-Tg)
• Thyroid Peroxidase Antibodies (Anti-TPO)
• Reverse T3 (rT3)

Let’s break down what these tests mean using our Thyroid Factory analogy.

The Factory Floor: T3 and T4 Production

The Thyroid Factory is staffed by workers called thyroglobulin (Tg) and thyroid peroxidase (TPO). These teams produce T3 and T4—the active and storage forms of thyroid hormone.

• Total T3/T4: Total number of hormones produced
• Free T3/FT4: Number of hormones actually available for use

Optimal Levels:

• FT3: 2.0–4.4 ng/mL (aim for higher end)
• FT4: 0.8–1.8 ng/dL (aim for higher end)

The Immune Attack: Thyroid Antibodies

Unfortunately, “hitmen” called anti-Tg and anti-TPO antibodies can attack your thyroid workers. These are produced by a confused immune system and can halt hormone production.

Optimal Levels:

• Anti-Tg: Under 35 IU/mL (aim for close to zero)
• Anti-TPO: Under 35 IU/mL (aim for close to zero)

When you have abnormal antibodies paired with low thyroid hormone, you likely have Hashimoto’s Thyroiditis—the most common cause of hypothyroidism.

The Control System: TSH Regulation

Your brain acts as CEO, communicating with the thyroid using TSH (thyroid-stimulating hormone).

• High TSH: Brain demands more thyroid hormone
• Low TSH: Brain signals to scale back production

Optimal Levels:

• TSH: 1.90–2.90 mIU/L (optimal for heart health)
• For women trying to conceive: Below 2.5 mIU/L (3, 5)

The Quality Check: Reverse T3

Sometimes the factory produces reverse T3 (rT3)—a defective version that doesn’t work properly. High levels can make you feel sluggish even with adequate thyroid production.

Optimal Levels: rT3: 10–24 ng/dL

Thyroid Lab Values Summary

Lab Test	Optimal Level	Notes
FT3	2.0–4.4 ng/mL	Aim for higher end
FT4	0.8–1.8 ng/dL	Aim for higher end
TSH	1.90–2.90 mIU/L	<2.5 for fertility
Anti-Tg	Under 35 IU/mL	Aim for close to zero
Anti-TPO	Under 35 IU/mL	Aim for close to zero
rT3	10–24 ng/dL	Within range

Preparing for Thyroid Testing

1. Stop biotin supplements 2 days before testing—they can interfere with results (6)
2. Consider stopping all supplements 2-3 days before testing
3. If pregnant or on birth control, ensure your doctor tests TSH and FT4, as estrogen can affect total T4/T3 (7)

Important Considerations

Optimal thyroid levels can vary by age, sex, and life stage:

• Women are 5-8 times more likely to develop hypothyroidism than men (2)
• Older adults naturally have higher TSH and lower T4
• Pregnant individuals have different optimal ranges
• Ethnic differences exist—Black Americans typically have lower TSH than White or Mexican Americans

Most importantly: Your symptoms matter. If your labs are “normal” but you feel awful, you may still have a thyroid issue that needs attention.

Next Steps After Diagnosis

If you’ve been diagnosed with hypothyroidism, don’t worry—this is a manageable condition. Work closely with your dietitian and endocrinologist to:

• Follow your treatment plan
• Make dietary adjustments
• Stay active
• Manage stress
• Attend regular check-ups

Remember that medication adjustments may be needed over time. A personalized approach ensures treatment addresses not only your lab numbers but also how you feel.

For more guidance on living with hypothyroidism, check out our comprehensive guide: Fuel Your Thyroid: What is a Hypothyroidism Diet?

References

1. Surks M. Clinical manifestations of hypothyroidism - UpToDate. October 2024.
2. Ross D. Diagnosis of and screening for hypothyroidism in nonpregnant adults - UpToDate. October 2024.
3. Xu Y, et al. The optimal healthy ranges of thyroid function defined by cardiovascular risk. Lancet Diabetes Endocrinol. 2023.
4. Wartofsky L, Dickey RA. The evidence for a narrower thyrotropin reference range. J Clin Endocrinol Metab. 2005.
5. Thyroid status and risk of miscarriage. American Thyroid Association.
6. American Thyroid Association. Thyroid Function Tests.
7. Smith P. The “new normal” for thyroid function test ranges. Clinical Thyroidology. 2024.
8. Almandoz JP, Gharib H. Hypothyroidism: etiology, diagnosis, and management. Med Clin North Am. 2012.