Table 1.

Deiodinase expression in human tissue and its role in normal tissue function as well as in hyper- and hypothyroid states.

Tissue	Deiodinase Expression	Normal Function	Hyperthyroidism	Hypothyroidism
Thyroid Liver Kidney Skeletal muscle	D1	Production of T3 into plasma	Increased function	Decreased function
Brain	D2	Production of T3 into plasma and local tissues	Decreased function	Increased function
Placenta Brain	D3	Degradation of T3	Increased function	Decreased Function

T3: thyroxine.