Healthy Thyroid Gland Function

What is Reverse T3 Dominance?

While borderline low thyroid function is becoming more widely accepted by the medical profession, reverse T3 dominance is often overlooked.

Reverse T3 dominance, sometimes referred to as Wilson’s Syndrome is a common hypothyroid (low thyroid function) problem. It is a condition where hypothyroid symptoms exist, but circulating levels of T3 and T4 appear to be within normal test limits.

What is actually happening is T4 is no longer converting to T3, but is being shunted towards the production of inactive ‘reverse T3′ (rT3).

rT3 slows metabolism and causes the typical signs & symptoms of hypothyroidism.

What Causes Reverse T3 Dominance?

Prolonged stress and toxicity are the major causes of reverse T3 dominance.

Unrelenting stress results in high levels of cortisol, the main hormone released by the adrenal glands in response to stress. Elevated cortisol inhibits conversion of T4 into T3, reducing active T3 levels. T4 is instead converted to rT3.

Reverse T3 dominance may persist even when your stress levels settle down and cortisol levels return to normal. This is because the rT3 continues to inhibit the conversion of T4 to T3, perpetuating production of the inactive T3 hormone.

Toxins such as agricultural chemicals, heavy metals and industrial pollutants selectively affect thyroid gland homeostasis and function. These toxins disrupt normal thyroid hormone action.

Reverse T3 Blocks Active T3

rT3 has the same molecular structure as T3 however it is a mirror image of T3 and therefore fits into the receptor upside down. This prevents the active T3 from binding to the receptor site and activating the appropriate thyroid response.

Reverse T3 Testing

If you suspect you have a sluggish or under active thyroid it is recommended that ask your health practitioner to perform a comprehensive thyroid function test.

This includes measuring Thyroid Stimulating Hormone (TSH), free T4, free T3 and rT3. This will assist an accurate diagnosis of actual thyroid function.

Currently most doctors only test (TSH) levels due to restraints within the current medical model.

You may be told that your thyroid function is normal when TSH levels are within an acceptable range. Unfortunately having normal TSH levels does not automatically rule out a hypothyroid condition.

A single test of Thyroid Stimulating Hormone (TSH) does not reflect how much T4 and T3 is being produced.

In addition, it does not assess how well T4 is converting to the active T3 form. In fact, it may not be converting at all, it may be converting to inactive rT3.

A measurement of rT3 is valuable in identifying a Reverse T3 Dominance.

The Natural Thyroid Diet has information on investigating and treating reverse T3 dominance.