What Does a High Reverse T3 Mean?
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A high reverse T3 means most of your T4 is converting into an inactive form that sits on your T3 receptors without activating them — so you can have all the signs of hypothyroidism even when your other thyroid hormones are in the “normal range.”
What reverse T3 is
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.”
What raises reverse T3
Things that cause you to increase rT3 levels are illness, starvation and excessive cortisol (stress). rT3 slows down metabolism and it's theorized to aid in survival. Interestingly, hibernating bears have high rT3 levels.
Finding the cause
I find the rT3 is often coming from adrenal dysfunction (stress), but we also need to consider nutrient deficiencies.
Lowering reverse T3
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.
About the author
Allen Smolenski, M.D.
Emergency Medicine physician and founder of Coastal Medical Clinic in Surfside Beach (2009). After losing nearly 60 pounds himself — and placing third in his class at the 2008 NPC Natural Northern USA Bodybuilding Contest — he completed a fellowship in Anti-Aging and Regenerative Medicine through the A4M, and now helps patients across the Grand Strand optimize their hormones, metabolism, and long-term health.
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