Frequently Asked Questions
RT3 is a metabolite (small molecule) of T4 (thyroxine). Typically T4 converts to T3 conversion - it becomes triiodothyronine (T3), the active thyroid hormone. But in some cases, the body conserves energy by converting the T4 instead into rT3, an inactive form of T3 that is incapable of delivering oxygen and energy to the cells, as T3 does. Measuring Reverse T3 or rT3 can be measured by a blood test.
Reverse T3 is kind of a hibernation hormone, in times of stress and chronic illness, it lowers your metabolism. So many people seemingly have normal thyroid levels, but if they have high Reverse T3, they're actually suffering from hypothyroidism.
As mentioned, conventional endocrinology assumes that in most people, the T4 to T3 conversion process functions seamlessly, and that the presence of elevated rT3 is not evidence of any thyroid dysfunction.
Integrative hormone doctors, however, have a different view of the role and value of rT3 and believe that elevated levels of rT3 , even though TSH, Free T3 and Free T3 values may be within the normal reference range, reflect a thyroid problem at the CELLULAR LEVEL - a condition that Kent Holtorf, MD , a thyroid expert calls "cellular hypothyroidism."
According to integrative doctors elevated RT3 can be triggered by ongoing chronic, physical or emotional stress, adrenal fatigue, low ferritin (stored iron) levels, acute illness and injury, and chronic disease, amongst other factors.
Reverse T3 is actually an "antithyroid". T3 is the active thyroid that goes to the cells and stimulates energy and metabolism. Reverse T3 is a mirror image, it goes to the receptors, sticks there, and nothing happens, blocking the thyroid effect.
Reverse T3 can be seen as a hibernation hormone, in times of stress and chronic illness, it lowers your metabolism. So many people seemingly have normal thyroid levels, but if they have high Reverse T3, they're actually suffering from hypothyroidism.
A study in The Journal of Clinical Endocrinology & Metabolism found that TSH and/or T4 levels can be poor indicators of the actual thyroid levels in tissues, and therefore, in a substantial percentage of patients, do not reflect whether or not a person has truly normal thyroid levels.
A Reverse T3 level above 150, or a free T3/reverse T3 ratio that exceeds 0.2 [when the Free T3 is measured in picograms per milliliter (pg/mL)] - may indicate hypothyroidism.
Reverse T3 is an excellent marker for reduced cellular T4 and T3 levels not detected by TSH or serum T4 and T3 levels.
High or high normal rT3 is not only an indicator of tissue/cell hypothyroidism, but also that replacement of T4 only (for example Eltroxin), would not be considered optimal in such cases and would be expected to have inadequate or sub-optimal results.
A high reverse T3 demonstrates that there is either:
- An inhibition of reverse T3 uptake into the cell, and/or
- There is increased T4 to reverse T3 formation
According to integrative practitioners, one of the key ways to address elevated rT3 and "cellular hypothyroidism" is through thyroid treatment with a medication that contains T3 such as Tertroxin, and in other cases T3 is added to a synthetic T4 prescription drug (i.e. Eltroxin).
Patients who are interested in rT3 testing may find it difficult to find a doctor willing to run these tests, or treat any imbalances. Many conventional doctors do not test for T3 and rT3, or they prescribe T3 medications, and this may not be a good choice for those patients. Instead, an integrative doctor such as our Health Renewal doctors , who acknowledge the significance of rT3 may be needed. Patients with high rT3 according to their blood results would be treated with T3 as well.
An appointment with one of our Health Renewal doctors will include a thyroid questionnaire and thyroid blood tests (including rT3, amongst other tests, to assess your thyroid status.