COMPENDIUM ON FUNCTIONAL MEDICINE - Flipbook - Page 160
● Type I deiodinase (D1)
Found primarily in liver, kidney, and thyroid; responsible for
producing most of the circulating T3
● Type II deiodinase (D2)
Present in the brain, pituitary, brown adipose tissue, and skeletal
muscle; provides local T3 for tissue-specific needs
● Type III deiodinase (D3)
Located in brain, placenta, and fetal tissues; primarily inactivates
T4 by converting it to reverse T3 (rT3)
The balance between these enzymes determines the relative
production of active T3 versus inactive reverse T3, which has
significant implications for cellular metabolism [7].
Physiological Effects of Thyroid Hormones
Thyroid hormones influence virtually every cell and system in the
human body. Their primary effects include:
Metabolic Regulation
● Increase basal metabolic rate
● Enhance oxygen consumption and heat production
● Stimulate glucose metabolism (absorption, glycolysis,
gluconeogenesis)
● Promote lipolysis and lipid metabolism
● Accelerate protein synthesis and turnover
Developmental Effects
● Essential for brain development during fetal and early
postnatal periods
160
