**Core Concept**
Thyroxine (T4) is a hormone produced by the thyroid gland, and its biosynthesis involves the iodination and coupling of tyrosine residues in thyroglobulin. The thyroid gland's ability to synthesize T4 is essential for regulating various physiological processes, including metabolism and growth.

**Why the Correct Answer is Right**
Thyroxine is synthesized from tyrosine through a series of enzyme-catalyzed reactions. The process begins with the iodination of tyrosine residues in thyroglobulin, followed by the coupling of these iodinated tyrosines to form T4. This process is catalyzed by the enzymes thyroid peroxidase and thyroperoxidase. The resulting T4 molecule is then stored in the thyroid gland and released into the bloodstream in response to thyroid-stimulating hormone (TSH) from the pituitary gland.

**Why Each Wrong Option is Incorrect**
**Option A:** Arginine is not directly involved in the synthesis of thyroxine. While arginine is an essential amino acid, it serves different roles in the body, such as nitric oxide production and protein synthesis.
**Option B:** Lysine is also not directly involved in thyroxine synthesis. Lysine is an essential amino acid involved in protein synthesis and various cellular processes, but it is not a precursor for T4 production.
**Option C:** Methionine is a sulfur-containing amino acid that plays a role in various metabolic pathways, including the synthesis of cysteine and homocysteine. However, it is not directly involved in the synthesis of thyroxine.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the thyroid gland's ability to synthesize T4 is dependent on adequate dietary iodine intake. Iodine deficiency can lead to goiter, hypothyroidism, and cretinism in severe cases. Therefore, iodized salt is often used to prevent iodine deficiency disorders.

**✓ Correct Answer: D. Tyrosine**