Thyroid hormone controls your energy, growth and metabolism. The thyroid gland sits in the front part of the neck and makes thyroid hormone from iodine and an amino-acid called tyrosine. 80% of thyroid output is tyrosine with 4 iodine molecules attached, called T4, but this is not the active thyroid hormone.
Outside the thyroid gland, especially in the muscle, liver, kidney and brain, T4 must have one of its iodine molecules removed to form the active thyroid hormone, called T3, which is the form that gets into the cells to do its work. Thyroid binds to nuclear receptors and commands a whole array of energetic and building processes, from growth and metabolism, to energy production and detoxification.
About 1% of T4 converts to a “mirror image” sort of T3 called reverse T3, which will bind to thyroid receptors but NOT activate them, meanwhile blocking the active T3 from binding and activating receptors. Reverse T3 also downregulates thyroid receptors effectively lowering thyroid function.
Under times of stress or high cortisol more T4 converts to the reverse T3 form, then once conditions return to normal the conversion to reverse T3 returns to a normal amount. Sometimes people get “stuck” making too much reverse T3. Inflammation also drives reverse T3 formation.
If someone is on thyroid medication and has a healthy T3 level, but still has low thyroid symptoms, it’s time to check reverse T3. If they have a relatively high reverse T3 level then they may need a T3 only form of thyroid since giving them anything with T4 in it would just convert to more reverse T3. In this case one should also consider the underlying causes of high reverse T3 and especially work to lower cortisol, namely to lower stress or inflammation in the body.
Scott Rollins, MD, is Board Certified with the American Board of Family Practice and the American Board of Anti-Aging and Regenerative Medicine. He specializes in bioidentical hormone replacement for men and women, thyroid and adrenal disorders, fibromyalgia and other complex medical conditions. He is founder and medical director of the Integrative Medicine Center of Western Colorado (www.imcwc.com) and Bellezza Laser Aesthetics (www.bellezzalaser.com). Call (970) 245-6911 for an appointment or more information.