Question

The synthesis of thyroxine T4 in the human body requires .............

• A. Selenium
• B. Iodine
• C. Iron
• D. Zinc

Hint:

Iodine deficiency leads to goiter and hypothyroidism due to reduced thyroxine (T4) production.

Answer 1

The Correct Option is B

Step 1: Recall the structure of thyroxine (T4).
Thyroxine (T4) and triiodothyronine (T3) are thyroid hormones derived from tyrosine. They contain iodine atoms as an essential structural component.
Step 2: Mechanism of synthesis.
- Tyrosine residues in thyroglobulin are iodinated by the enzyme thyroid peroxidase. - Iodine atoms are incorporated at specific positions of tyrosine, forming mono- and di-iodotyrosine. - Coupling of two iodinated tyrosines forms T3 or T4.
Step 3: Eliminate incorrect options.
- Selenium: important for deiodinase enzymes (converts T4 → T3), but not required for T4 synthesis itself. - Iron: required in hemoglobin, electron transport enzymes, but not in T4 synthesis. - Zinc: involved in transcription factors, not thyroid hormone production.
Step 4: Conclude.
The correct essential element for thyroxine synthesis is iodine. Final Answer: \[ \boxed{\text{Iodine}} \]