Inhibition of pituitary type 2 deiodinase
by reverse triiodothyronine does not alter thyroxine-induce inhibition of thyrotropin secretion in hypothyroid rats.
Some well-known selenoproteins, in which Se is an essential trace element for their activity, are glutathione peroxidase, thioredoxin reductase, iodothyronine deiodinase
, selenoprotein P, selenoprotein W, selenoprotein N (Beckett and Arthur, 2005; Lescure et al.
Baumgartner and colleagues (1997) found that the activity of 5'H deiodinase
was elevated in the frontal cortex in both groups of rats.
This is dependent on production of T3 within the cells as polymorphisms of deiodinase
with reduced generation of T3 have a close association with resistance of insulin in diabetic patients.
Hemangioma and associated severe hypothroidism developing secondary to increased type tree iodothyronine deiodinase
was reported in 2000 for the first time (8).
Type 2 iodothyronine deiodinase
is upregulated in rat slow- and fast-twitch skeletal muscle during cold exposure," American Journal of Physiology--Endocrinology and Metabolism, vol.
It is because of increase in activity of deiodinase
D3, inactivating [T.
3,4] Placenta produces the enzyme deiodinase
, which increases the peripheral metabolism of thyroid hormones and regulates the transplacental transport of thyroid hormone and iodide.
On the other side, type 2 deiodinase
activity has been demonstrated in the mouse skeleton and is induced by vitamin D, suggesting a closer relationship between thyroid hormones and vitamin D .
23,24 Furthermore, reduced deiodinase
activity in ESS could hamper marginal conversion of T4 to T3.
An emerging concept in this field is that TH s pleiotropic actions can be amplified or attenuated at cell level by the deiodinase
enzymes that can increase (D2) or decrease (D3) the active TH concentration regardless of hormone plasma levels.
This supply of TH to the fetus, as well as increased concentrations of TH binding proteins (thyroxine-binding globulin) and degradation of TH by placental type 3 iodothyronine deiodinase
necessitate an increased production of maternal TH (1, 2).