Among the controversial issues surrounding combination T4/T3 therapy for hypothyroidism is the choice of the best biochemical parameter by which to monitor therapy. This article explores the potential use of reverse T3 (rT3) for this role.

Jul 11, 2024 · Reverse T3 is a metabolite (byproduct) of T4. Typically, when T4 loses an atom of iodine—a process known as monodeiodination —it becomes (T3), the active thyroid hormone. The body also converts T4 into rT3, which is 3,3',5'-triiodothyronine, an inactive form of T3 that is incapable of the metabolic activity normally carried out by T3.

Feb 3, 2022 · However, a different process can, and does, occur when an opposite, “mirror-image,” iodine is cleaved from T4 and the result is called reverse T3, or RT3. RT3 is interesting because it blocks T3 from its functioning.

Oct 11, 2024 · In addition to the basic thyroid hormones (TSH, fT4, and fT3), additional thyroid markers can provide deeper insight into abnormal lab values and help identify the underlying causes of thyroid dysfunction. Reverse T3 (rT3) rT3 is an inactive byproduct produced during the conversion of T4 into T3.

In critically ill patients, rT3 can be high while TSH, T3, and T4 can be normal or low. There is controversy with respect to combination T3-T4 supplementation to treat the thyroid disease. TeleTest offers the option to test for rT3 but we do not use this lab value to guide medical decision-making.

Mar 10, 2025 · Reverse T3 – Reverse T3 is an anti-thyroid metabolite that acts to completely BLOCK your thyroid from working. Reverse T3 is created by the body from T4. Your body can either turn T4 into T3 or into reverse T3 based on what it needs.

Jan 1, 2017 · Most T3 is produced by enzymatic outer ring deiodination (ORD) of T4 in peripheral tissues. Alternative, inner ring deiodination (IRD) of T4 yields the metabolite rT3, the thyroidal secretion of which is negligible. Normally, about one-third of T4 is …

Feb 4, 2016 · Reverse T3 (rT3) is an inactive form of T3 that is produced in the body particularly during periods of stress. When the body is under stress, such as during a serious illness, it tries to prevent many tissues that depend on T3 from being metabolically active by producing more reverse T3 than T3.

Did you know that there are circumstances in life that will cause your body to start making excess RT3, aka reverse T3? It’s an inactive thyroid hormone and eventually lowers our free T3, the active hormone.

Mar 10, 2025 · It’s one of the most sensitive measures of thyroid function – the difference between your free T3 and your reverse T3 can identify thyroid dysfunction very early on and becomes abnormal long before other measures of thyroid function such as TSH and free T4.