Which hormone synthesized from Tyrosine?
**Core Concept**
The synthesis of hormones from amino acids involves a series of enzyme-catalyzed reactions that ultimately produce biologically active molecules. Tyrosine, an aromatic amino acid, serves as the precursor for several important hormones in the human body.
**Why the Correct Answer is Right**
Thyroid hormones are synthesized from tyrosine through a pathway involving iodination, oxidation, and coupling reactions. The enzyme thyroperoxidase (TPO) is responsible for iodinating tyrosine residues on thyroglobulin, which is then oxidized to form diiodotyrosine (DIT). Two DIT molecules are coupled to form thyroxine (T4), while a single DIT molecule can be coupled with iodine to form triiodothyronine (T3). The thyroid hormones T3 and T4 play crucial roles in regulating metabolism, growth, and development.
**Why Each Wrong Option is Incorrect**
**Option A:** Insulin is synthesized from proinsulin, which is a precursor protein composed of A and B chains linked by disulfide bridges. Insulin is produced in the pancreas and plays a vital role in glucose metabolism.
**Option B:** Adrenaline (epinephrine) is synthesized from the amino acid phenylalanine, not tyrosine. It is produced in the adrenal medulla and plays a key role in the body's "fight or flight" response.
**Option C:** Growth hormone is produced by the pituitary gland and is involved in regulating growth, metabolism, and body composition. While it is synthesized from a precursor protein, it is not derived from tyrosine.
**Clinical Pearl / High-Yield Fact**
Thyroid hormone synthesis is dependent on adequate iodine intake, and iodine deficiency can lead to hypothyroidism and cretinism in severe cases.
**Correct Answer: C. Growth hormone is produced by the pituitary gland and is involved in regulating growth, metabolism, and body composition. While it is synthesized from a precursor protein, it is not derived from tyrosine.