ENDOCRINE SYSTEM
THYROID FOLLICULAR CELL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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D1
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D2
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D3
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it is converted by all of these deiodinases
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Detailed explanation-1: -T4 is converted into T3, the active form of thyroid hormone, by two enzymes called deiodinases. People with hypothyroidism are treated with a synthetic T4 hormone, which the enzymes convert to T3. This treatment is usually effective, but some people continue to have symptoms even after treatment.
Detailed explanation-2: -Amiodarone, other iodinated compounds (cholecystographic agents: ipodate and iopanoic acid), propylthiouracil and propranolol are known to act in this way.
Detailed explanation-3: -In the pituitary, 80–90% of T4 is converted to T3, while only about 30–50% of T4 in the peripheral tissue is converted to active T3. This is due to the inefficiency of D1 and the presence of D3 in all tissues of the body except the pituitary that competes with D1 and converts T4 to reverse T3.
Detailed explanation-4: -Type 1 and type 2 deiodinase (D1 and D2) convert T4 into T3 whereas D3 degrades T4 and T3 into inactive metabolites and is thus the major physiological TH inactivator.