Reverse T3 Dominance - A Thyroid Imbalance

In a healthy patient a normal thyroid gland secretes all of the circulating T4 and about 20% of the circulating T3. The T4 made by the thyroid gland circulates throughout the body and is converted into T3 and a tiny amount of reverse T3 in the kidneys, brain and fat tissue. Most of the biological activity of thyroid hormones is due to T3. It has a higher affinity for thyroid receptors and is approximately 4 - 10 times more potent than T4. Because 80% of serum T3 is derived from T4 in tissues such as the liver and kidney, T4 is considered a pro-hormone. Reverse T3 has no thyroid action what so ever except it binds to T3 receptors blocking the action of T3. In normal patients T3 dominates and reverse T3 usually makes up less than 10% of total T3 levels and is therefore no problem.

Reverse T3 dominance or “Wilson’s Syndrome” is a condition identified by Dr Denis Wilson that exhibits most hypothyroid symptoms although circulating levels of T3 and T4 are within normal test limits. It is a condition of thyroid hormone imbalance rather than a simple deficiency. Periods of prolonged stress may cause an increase in cortisol levels as the adrenal glands respond to the stress. The high cortisol levels inhibit the conversion of T4 into T3 thus reducing active T3 levels. The conversion of T4 is then shunted towards the production of the inactive reverse T3. This reverse T3 dominance may persist even after the stress passes and cortisol levels have returned to normal as the reverse T3 itself may also inhibit the conversion of T4 to T3 thus perpetuating the production of the inactive reverse T3 isomer. There is some argument to this last point with some research indicating that the elevated rT3 is only temporary and not permanent as Dr Wilson describes and hence questions his theory altogether. Which ever the case may be we have had many patients whom have benefited from his protocol.

Reverse T3 has the same molecular structure as T3 however its three dimensional arrangement (stereochemistry) of atoms is a mirror image of T3 and thus fits into the receptor upside down thus preventing the active T3 binding to the receptor and activating the appropriate thyroid response. Unfortunately blood tests for T3 measure both normal T3 and reverse T3 levels as it is unable to distinguish between the two. Thus T3 levels may appear normal however a significant proportion of this may be due to the presence of the inactive reverse T3 isomer giving a false impression of true thyroid function. To overcome this diagnostic problem there is a special test that specifically measures reverse T3 alone and should be requested to rule out reverse T3 dominance. Ideally reverse T3 should be between 200-300 pmol/L and if found to be above 400 pmol/L indicates the presence of reverse T3 dominance. If reverse T3 dominance is diagnosed it may be treated by supplementing T3 once adrenal exhaustion, hypoglycemia and/or low sex hormone levels have been ruled out and/or treated.

It is important that no T4 (thyroxine), including Armour Thyroid, is used for this condition as some of the supplemented T4 will only be converted into reverse T3 and keep this cycle going. The idea is to use T3 to provide thyroid activity to alleviate symptoms and to also suppress TSH production which in effect reduces the bodies own production of T4. With little or no T4 left in the system reverse T3 can no longer be produced and eventually whatever is already present in the body will be eliminated thus reducing reverse T3 levels. The conversion of T4 into T3 will then no longer be inhibited by the reverse T3 allowing the appropriate activation of T4 into the active T3 form to occur.

NB: It is also very important that if elevated levels of cortisol are found (stage 1 adrenal exhaustion) it should be treated first because if it is left elevated it will only continue to inhibit the conversion of T4 into T3 and thus continue reverse T3 production and thus cause this treatment to potentially fail. In addition some patients respond poorly to the treatment described below until any adrenal imbalances are rectified. Therefore we recommend any adrenal imbalance be corrected before commensing this treatment.

Treatment

Slow release T3 capsules work best in this situation. Begin by taking 7.5mcg of T3 as a slow release capsule morning and night. Symptoms should be monitored for improvement in energy levels and an increase in body temperature (ideally underarm temperature above 36.5C). Dose should be gradually increased by 7.5mcg increments every 5 days until symptoms are alleviated and/or body temperature is back to normal.

Symptoms for hyperthyroid such as sweating, anxiety, palpitations, etc must also be monitored for and doses reduced at the first sign of these symptoms appearing. Care should be taken not to allow the pulse rate to remain above 100 beats / minute, or more than about 20 beats / minute faster than before treatment. The dose should be reduced to the highest dose possible where these symptoms do not occur. Usually we find total daily doses of T3 required to be as high as 90 to 100mcg per day before body temperature and symptoms are restored back to normal. Once the correct dose has been obtained the dose should be maintained for four weeks and then the dose gradually reduced by 7.5mcg increments every 3 days until off it completely. By this stage TSH should return to normal thus stimulating T4 production which then, if the treatment was successful, should be converted into the active T3 form. Follow up blood tests for T3, T4 and reverse T3 should all be in the ideal range. Sometimes this protocol needs to be repeated several times if initially unsuccessful.

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