What does a high reverse T3 mean?

Coastal Medical Clinic - Myrtle Beach, SC.

If your labs show a high reverse T3 level this means that you are converting most of your T4 into reverse T3. Reverse T3 is an isomer of T3. If you recall T3 is the most active form of thyroid and it is converted from T4 as needed. The problem with rT3 is that it will bind to T3 receptors but it has no activity so high rT3 levels can give you signs of hypothyroidism even though the other thyroid hormones are in the "normal range".

Things that cause you to increase rT3 levels are illness, starvation and excessive cortisol (stress). rT3 slows down metabolism and its theorized to aid in survival. Interestingly hibernating bears have high rT3 levels.

In your case I think the rT3 is coming from adrenal dysfunction (stress) but we also need to consider nutrient deficiencies. One of the treatments for high rT3 is to place you on a sustained release T3 for 2 or 3 months the negative feedback to the pituitary will slow down the production of T4 and hence will slow down the production of rT3. You will feel better with lower rT3 levels since T3 will be able to bind unopposed to receptors.