The Thyroid Myth: Why Your ‘Normal’ Labs Don’t Tell the Full Story
- Catherine Brigger
- Feb 16
- 3 min read
The Frustration of Unexplained Symptoms
Have you ever been told your thyroid labs are normal, yet you still struggle with fatigue, weight gain, hair thinning, depression, or brain fog? You’re not alone. Many patients experience classic symptoms of hypothyroidism but are dismissed because their thyroid-stimulating hormone (TSH) test falls within the so-called ‘normal’ range.
The truth is, conventional medicine often fails to evaluate thyroid function comprehensively. Doctors routinely test TSH and sometimes T4 (thyroxine), but these markers don’t always reflect how well your body is actually using thyroid hormones. To get the full picture, we need to look deeper—specifically at Free T3 and Reverse T3 (rT3).
Why TSH Alone Isn’t Enough
TSH is a hormone released by the pituitary gland that signals the thyroid to produce T4, the inactive form of thyroid hormone. However, T4 itself must be converted into T3 (triiodothyronine), the active form that fuels metabolism and energy production.
Unfortunately, many conventional doctors overlook Free T3 (FT3), the hormone that actually determines how your body feels and functions. A normal TSH doesn’t guarantee that enough T3 is being produced or that it’s reaching your cells effectively.
Additionally, Reverse T3 (rT3) acts as a metabolic brake, competing with Free T3 for receptor sites. If rT3 levels are too high, it can block the beneficial effects of T3, leading to symptoms of hypothyroidism even when TSH appears ‘normal.’
Key Takeaway:
TSH does NOT measure active thyroid hormone levels.
T4 is inactive and must convert to T3 for real benefits.
Free T3 is the most important marker of thyroid function.
High Reverse T3 can block thyroid activity and cause hypothyroid symptoms.
Why Conventional Medicine Fails Patients
Most traditional doctors only prescribe T4 medications like Synthroid or levothyroxine, assuming the body will convert it into T3 efficiently. But many patients have issues with conversion due to stress, inflammation, nutrient deficiencies, and chronic illness.
Without assessing Free T3 and Reverse T3, these patients continue to feel unwell despite being on medication. A functional medicine approach recognizes that not all patients convert T4 to T3 efficiently and that many require direct T3 supplementation (such as liothyronine or natural desiccated thyroid medications like Armour Thyroid or NP Thyroid).
Why Functional Thyroid Testing is Essential
A truly comprehensive thyroid panel should include:
TSH – (Not the only marker that matters!)
Free T4 (FT4) – Measures inactive thyroid hormone levels.
Free T3 (FT3) – Shows how much active thyroid hormone is available.
Reverse T3 (rT3) – Identifies thyroid hormone dysfunction at the cellular level.
Thyroid Antibodies (TPO, TG Ab) – Screens for Hashimoto’s or autoimmune thyroid disease.
The Solution: A Functional Medicine Approach
At TRUE Rejuvenation, we take a root-cause approach to thyroid health. We use advanced testing to assess not just thyroid hormone levels, but also conversion issues, nutrient deficiencies, and adrenal function—all of which impact how your thyroid functions.
If you’ve been told your thyroid is ‘fine’ but still feel exhausted, unable to lose weight, or mentally foggy, it’s time for a deeper evaluation. You deserve to feel energized, balanced, and fully alive.
Are You Ready to Feel Better?
Book a comprehensive thyroid consultation today and discover how optimizing Free T3 and Reverse T3 levels can help you regain your energy and metabolism!
References:
Bianco, A. C., et al. (2019). "Biochemistry, Physiology, and Pathophysiology of the T4 to T3 Conversion Pathway." Endocrine Reviews.
Wiersinga, W. M. (2018). "Clinical Relevance of TSH, Free T4, and Free T3 Measurements in Hypothyroidism." European Thyroid Journal.
Peeters, R. P., et al. (2015). "The Role of Thyroid Hormone in Metabolism." Nature Reviews Endocrinology.
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