Thyroxine & Vitamin D

Thyroxine & Vitamin D

“How does vitamin D maintain bone health? FAQ explained”

Question 1. Synthesis of thyroxine 
Answer: 

• Thyroxine is a thyroid hormone
• It is synthesized from the tyrosine residues of the protein thyroglobulin & activated iodine
• The tyrosine of thyroglobulin is first iodinated at position 3 to form monoiodotyrosine
• Next, it is iodinated at position 5 to form diiodotyrosine
• Later two molecules of diiodotyrosine couple to form thyroxine T4
• As the process of iodination is completed, each molecule of thyroglobulin contains about 6-8 molecules of thyroxine

“Understanding thyroxine and vitamin D through FAQs: Composition, functions, and uses explained”

Question 2. Mechanism of action of vit D 
Answer:

1. Action on the intestine

In intestinal cells, calcitriol binds with cytosolic receptors
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Forms calcitriol – receptor complex
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Complex enters the nucleus of the cell
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Interacts with DNA
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This leads to the synthesis of calcium-binding protein
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This protein increases calcium uptake by the intestine

“Importance of studying thyroxine and vitamin D for medical students: Questions explained”

2. Action on bones

• Increases calcium deposition in osteoblasts

3. Action on kidneys

• Minimizes excretion of calcium and phosphorous