deiodinaas

Deiodinase is a family of enzymes crucial for thyroid hormone metabolism. These enzymes are responsible for removing iodine atoms from iodothyronines, the thyroid hormones thyroxine (T4) and triiodothyronine (T3). This process is essential for regulating the activity and bioavailability of thyroid hormones throughout the body.

There are three main types of deiodinases: type I (D1), type II (D2), and type III (D3). D1 is found primarily in the liver, kidneys, and thyroid gland, and it can catalyze both outer ring deiodination (converting T4 to the more active T3) and inner ring deiodination (converting T4 to the inactive reverse T3, or rT3). D2 is predominantly located in the brain, pituitary gland, brown adipose tissue, and skeletal muscle. Its main function is to generate T3 from T4, thus controlling local thyroid hormone levels in these sensitive tissues. D3 acts as an inactivator of thyroid hormones, primarily found in fetal tissues, the brain, and skin. It converts T4 and T3 into inactive metabolites, thereby preventing excessive thyroid hormone action during critical developmental periods or in specific tissues.

The activity of deiodinases is tightly regulated and influenced by various factors, including nutritional status, temperature, and hormonal signals. This regulation allows the body to fine-tune thyroid hormone levels to meet physiological demands, affecting metabolism, growth, and development. Defects in deiodinase function can lead to thyroid hormone resistance syndromes or other metabolic disturbances.