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Type 2 iodothyronine deiodinase is highly expressed in human thyroid
D Salvatore1, H Tu, J W Harney
1Thyroid Division, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
The Journal of Clinical Investigation
|August 15, 1996
Summary
Type 2 iodothyronine deiodinase (D2) is highly expressed in the human thyroid, contributing significantly to T3 production. This enzyme plays a key role in thyroid hormone regulation, especially in conditions like Graves' disease.
Area of Science:
- Endocrinology
- Molecular Biology
- Thyroid Research
Background:
- Type 2 iodothyronine deiodinase (D2) is crucial for intracellular T3 supply.
- D2's presence and role in the human thyroid were previously unevaluated.
Purpose of the Study:
- To investigate the expression and activity of D2 in the human thyroid.
- To compare D2 expression with Type 1 deiodinase (D1) in various thyroid conditions.
Main Methods:
- Quantification of D2 mRNA levels in human thyroid tissues.
- Assay of D2 enzyme activity in thyroid microsomes.
- Comparison of D2/D1 mRNA ratios in normal, stimulated, and diseased thyroid glands.
Main Results:
- D2 mRNA levels in the human thyroid are 50-150 fold higher than in the placenta.
- D2 mRNA expression is significantly elevated in Graves' disease and follicular adenomas.
- D2 activity is present in thyroid microsomes, distinct from D1, and contributes significantly to T4 to T3 conversion, especially in stimulated thyroids.
Conclusions:
- Intrathyroidal D2 activity significantly contributes to T3 production, particularly in Graves' disease and toxic adenomas.
- Differential regulation of D1 and D2 expression suggests distinct roles in thyroid hormone homeostasis.
- D2 may play a critical role in thyroidal T3 production during iodine deficiency.
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