If you had blood work done, your doctor looked at your TSH, said it was normal and closed the subject, yet you still feel tired, gain weight for no clear reason, lose hair, struggle with constipation, brain fog and feeling cold all the time, this article is for you.
After 25 years of treating patients with thyroid dysfunction, I can say with confidence: TSH is only the front door. Stopping there is like assessing an airplane engine by looking only at the temperature gauge.
What TSH is and why it isn't enough
TSH (thyroid-stimulating hormone) is produced by the pituitary gland and works as a command signal sent to the thyroid. When the thyroid is producing too little hormone, the pituitary raises TSH to push it to produce more. When it produces too much, TSH drops.
The problem is that this feedback mechanism can appear to be working fine while the thyroid still makes enough hormone to keep TSH within the reference range, even though the hormone it makes may not be reaching the cells and working properly inside them. TSH measures the command signal, not the hormone's action in the target tissue.
The markers that really need to be checked
In my clinical practice, a complete thyroid panel always includes:
- Free T4: the hormone produced directly by the thyroid. It can be low even when TSH is normal.
- Free T3: the active hormone, responsible for the real metabolic action in the cells. Many patients have a normal T4 but convert it poorly into T3.
- Reverse T3: an inactive form of T3 that competes with active T3 for the cell receptors. It rises with chronic stress, inflammation and severe dieting, and causes classic hypothyroid symptoms with a normal TSH.
- Anti-TPO (TPO antibodies): a marker of thyroid autoimmunity. It can be elevated years before any change in TSH. It is the diagnostic marker for Hashimoto's thyroiditis.
- Anti-TG: the second autoimmunity marker. In about 30% of Hashimoto's cases, anti-TPO is negative but anti-TG is elevated. Testing only one of them means missing the diagnosis in up to a third of patients.
The concept of functional hypothyroidism
There is a condition that conventional medicine often overlooks: functional hypothyroidism. The patient has a TSH within the lab's reference range but a free T3 in the lower third of the normal range, an elevated reverse T3, classic hypothyroid symptoms and, often, a positive anti-TPO pointing to an active autoimmune process.
In that situation, reporting the test as normal and sending the patient home without further investigation is a clinical mistake. The lab reference range for TSH was built from population statistics, and it includes people with undiagnosed Hashimoto's, subclinical dysfunction and other conditions that should have been left out of that sample.
What to ask your doctor at your next appointment
If you have symptoms consistent with hypothyroidism and want a complete evaluation, ask your doctor for: ultrasensitive TSH, free T4, free T3, reverse T3, anti-TPO and anti-TG. If your doctor refuses to order these tests because your TSH is normal, consider getting a second opinion from a practitioner who works with Functional Integrative Health. Your symptoms deserve a thorough investigation.
At the Dr. André Azevedo Clinic in Campinas, Brazil, we perform a complete functional thyroid evaluation, including all the markers described above, an analysis of peripheral T4-to-T3 conversion, an autoimmunity workup and an individualized protocol when needed. If you have symptoms that your conventional lab tests haven't adequately explained, we can help you find the real cause.
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