Endocrinology fundamentals — identify the catecholamine among the following hormones.

Introduction / Context:
Catecholamines are tyrosine-derived neurotransmitters/hormones (dopamine, norepinephrine, epinephrine) containing a catechol ring. Distinguishing them from peptide and steroid/iodothyronine hormones is a core classification skill.

Given Data / Assumptions:

• Norepinephrine is synthesized from dopamine via dopamine β-hydroxylase.
• FSH is a glycoprotein peptide hormone.
• Thyroxine (T4) is an iodinated amino acid derivative, but not a catecholamine.
• Tetrahydrofolate is a coenzyme, not a hormone.

Concept / Approach:
Identify the only option with a catechol nucleus (benzene ring with two adjacent hydroxyls) and known adrenergic activity.

Step-by-Step Solution:
Scan options for classical catecholamine names.Confirm norepinephrine as a sympathetic neurotransmitter/hormone.Eliminate peptide, iodothyronine, and cofactor choices.Select “Norepinephrine.”

Verification / Alternative check:
Physiology texts list norepinephrine as a primary catecholamine alongside epinephrine and dopamine.

Why Other Options Are Wrong:
FSH is peptidic; T4 lacks catechol structure; tetrahydrofolate is a vitamin cofactor.

Common Pitfalls:
Assuming all amino acid–derived hormones are catecholamines; iodothyronines are distinct.

Final Answer:
Norepinephrine.