3,5-Diiodothyronine (3,5-T₂) is an active thyroid hormone within the class of iodothyronines. It has two iodine atoms at positions 3 and 5 of its inner ring.

Biological effects

3,5-T₂ is an active thyroid hormone. It stimulates the TR-beta receptor for thyroid hormones and thus increases energy expenditure. It has agonistic (thyromimetic) effects at

myocardial Cardiac muscle (also called heart muscle, myocardium, cardiomyocytes and cardiac myocytes) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that ...

tissue and

pituitary In vertebrate anatomy, the pituitary gland, or hypophysis, is an endocrine gland, about the size of a chickpea and weighing, on average, in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain. The hypoph ...

, which results in 3,5-T₂ suppressing TSH release. 3,5-T₂ is an allosteric regulator of the

cytochrome c oxidase The enzyme cytochrome c oxidase or Complex IV, (was , now reclassified as a translocasEC 7.1.1.9 is a large transmembrane protein complex found in bacteria, archaea, and mitochondria of eukaryotes. It is the last enzyme in the respiratory elect ...

, the complex IV of the electron transport chain. It increases its activity by preventing the interaction of

adenosine triphosphate Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms o ...

(ATP) as an allosteric inhibitor.

Clinical significance

In nonthyroidal illness syndrome 3,5-T₂ concentrations are increased. This could explain why patients with low T3 syndrome don't benefit from substitution therapy with thyroid hormones.

References

External links

* {{DEFAULTSORT:Diiodothyronine, 3, 5- Iodinated tyrosine derivatives Thyroid Human hormones Hormones of the hypothalamus-pituitary-thyroid axis Hormones of the thyroid gland