Reverse Triiodothyronine (rT3)


This blood test measures levels of Reverse T3 (rT3). A Reverse Triiodothyronine (rT3) is a thyroid hormone that disrupts the activity of the active the form of thyroid hormone, triiodothyronine (T3). When thyroid hormone is functioning properly, thyroxine (T4) is converted to the active hormone (T3).

When reverse T3 is elevated, metabolic rhythms orchestrated by the active thyroid hormone (T3) act as if they were hit by a stun gun. Elevated levels of reverse T3 is also known as thyroid resistance because it mimics many of the same symptoms seen in those who suffer with low thyroid function (hypothyroidism). Some of those symptoms are fatigue, weight gain, cold hands, dry skin, hair loss, moodiness and a decline in cognitive function. Research has cited multiple factors that can generate an elevation in reverse T3. Some of those causes are: physical stress/trauma, strict dieting, chemical exposure, liver and kidney disease, severe illness, heavy metal toxicity, certain medications such as Propranolol (beta blockers), elevated cortisol, low iron levels, and lack of certain cofactors such as selenium and zinc which are crucial for healthy thyroid function.

Test Preparation For Optimal Results:

If possible, have the lab collected early in the morning or shortly after waking. For comparison purposes, have subsequent labs collected close to the same time.

Disclaimer: Your health care provider should evaluate a deviation from normal ranges.