Amino acid required for formation of thyroxine
**Core Concept**
Thyroxine (T4) is a hormone produced by the thyroid gland, and its synthesis involves the incorporation of iodine and an amino acid. The correct amino acid is crucial for the formation of thyroxine, and understanding this concept is essential for diagnosing thyroid disorders.
**Why the Correct Answer is Right**
Thyroxine is formed from the amino acid tyrosine. Tyrosine is a non-essential amino acid that serves as the backbone for the synthesis of thyroxine. The process involves the iodination of tyrosine residues on thyroglobulin, followed by the coupling of these residues to form thyroxine. This process is catalyzed by the enzyme thyroperoxidase. The correct incorporation of tyrosine is essential for the formation of thyroxine, which is then released into the bloodstream to regulate metabolism.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because tyrosine is not a non-essential amino acid for thyroxine synthesis.
**Option B:** This option is incorrect because phenylalanine is an essential amino acid but not directly involved in thyroxine synthesis.
**Option C:** This option is incorrect because tryptophan is an essential amino acid but not directly involved in thyroxine synthesis.
**Clinical Pearl / High-Yield Fact**
The incorporation of tyrosine into thyroxine is a highly specific process, and defects in this pathway can lead to congenital hypothyroidism.
**Correct Answer:** C. Tyrosine.