Sites of T4 to T3 Conversion in the Rat
Enzymatic T4 5′-monodeiodination has been demonstrated in a variety of rat tissues (1,2) and may be an important factor in the regulation of T3 concentrations in several target sites of thyroid hormone action. As a consequence, under various (patho)physiological conditions, the total T3 content of tissues which exhibit T4 to T3 conversion in vivo may be affected to an extent not disclosed by alterations in circulating T3 levels. In the present study, we evaluated the relationship between T3 in several extrathyroidal tissues and plasma T3 for both euthyroid and hypothyroid rats.
KeywordsBrown Adipose Tissue Anterior Pituitary Gland Hypothyroid State Thyroid Hormone Action Iopanoic Acid
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