Concept encyclopediaHormones
T3 (Triiodothyronine)
T3, triiodothyronine, liothyronine
Triiodothyronine (T3) is a metabolically active thyroid hormone that plays a crucial role in regulating metabolism, increasing mitochondrial consumption of oxygen, and promoting the conversion of cholesterol into youthful protective hormones. It is primarily produced in the liver through an enzymatic conversion from thyroxine (T4), with a majority of the body's T3 being produced outside of the thyroid gland .
T3 is more metabolically active than T4, and its production is influenced by the availability of glucose to the liver, allowing for a sensitive adjustment of metabolism to nutrition . When T3 is successfully converted from T4, it can be combined with low-density lipoprotein (LDL) and vitamin A in the mitochondria of the cell to form the "mother" pre-hormone, pregnenolone .
Research has shown that T3 has selective thyromimetic effects, mimicking the effects of T3 on serum thyroid-stimulating hormone (TSH) and growth hormone (GH) levels in rats . However, 3,5-diiodo-L-thyronine (T2) has also been found to have significant thyromimetic activity, although its effects are selective and different from those of T3 .
In hypothyroid states, a lower ratio of T4 to T3 is often more desirable, and some products, such as TyroMix, aim to provide a 2:1 or 3:1 ratio of T4 to T3 for research purposes . However, the production of T3 from T4 can be suppressed by thyroxine pills, making the problem worse if the liver is the main source of the thyroid problem .
Studies have also shown that the fraction of hormone or drug that is plasma protein-bound is readily available for transport through the brain endothelial wall, and that the free-hormone hypothesis is reconcilable with the observations of hormone transport through the blood-brain barrier .
In patients over fifty years of age with type II diabetes mellitus, serum T3 levels have been found to decline and rT3 levels to rise with worsening of metabolic control, indicating altered thyroid hormone metabolism in the uncontrolled diabetic state .
People also ask
- How is T3 produced in the body?The liver primarily produces T3 through an enzymatic conversion from thyroxine (T4).
- What happens when T3 is combined with LDL and vitamin A in the mitochondria?It can form the "mother" pre-hormone, pregnenolone, in the mitochondria of the cell.
- How does the ratio of T4 to T3 affect hypothyroid states?A lower ratio of T4 to T3 is often more desirable in hypothyroid states, and some products aim to provide a 2:1 or 3:1 ratio of T4 to T3.