deiodinaasit

Deiodinaasit are a family of enzymes that play a crucial role in thyroid hormone metabolism. These enzymes are responsible for catalyzing the removal of iodine atoms from thyroid hormones, primarily thyroxine (T4) and triiodothyronine (T3). This process is essential for regulating the biological activity of thyroid hormones.

There are three main types of deiodinases: type 1 (D1), type 2 (D2), and type 3 (D3). Each type has a specific tissue distribution and substrate preference, leading to different physiological functions. D1 is found mainly in the liver, kidneys, and thyroid gland, and it can activate T4 to T3 (outer ring deiodination) or inactivate T3 (inner ring deiodination). D2 is predominantly located in the brain, pituitary gland, brown adipose tissue, and skeletal muscle, and it primarily converts T4 to the more active T3 form. D3, found in the brain, placenta, and skin, acts to inactivate both T4 and T3 by removing an iodine atom from the inner ring, thus reducing thyroid hormone activity.

The activity of deiodinases is tightly regulated by various factors, including thyroid hormone levels themselves, selenium, and oxidative stress. By controlling the production and degradation of active thyroid hormones, deiodinases ensure that the body has the appropriate levels of these hormones to maintain metabolism, growth, and development. Dysregulation of deiodinase activity can contribute to thyroid disorders and other metabolic imbalances.