Which of the following hormones is a modified amino acid?

Appeared in: HPSSC - 2015

Explanation

Epinephrine is classified as an amino acid-derived hormone.
Specifically, it is a catecholamine, which is synthesized from the amino acid tyrosine through a series of enzymatic modifications.
This chemical structure makes it water-soluble and allows it to act rapidly by binding to receptors on the cell surface.

Option A: Estrogen is a steroid hormone, which is a lipid derived from cholesterol, not an amino acid.
Option B: Progesterone is also a steroid hormone synthesized from cholesterol. It is not derived from an amino acid.
Option D: Prostaglandins are eicosanoids, a class of lipids derived from the fatty acid arachidonic acid. They are not derived from amino acids.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Classification of hormones based on chemical structure as background academic context rather than a clinical decision trigger.
Understanding hormone classification is fundamental in pharmacology. For example, steroid hormones are lipid-soluble and can often be administered orally, while peptide hormones would be digested and must be injected.
Epinephrine's rapid action is due to its water-soluble nature and binding to cell surface receptors, making it a first-line treatment for life-threatening conditions like anaphylaxis and cardiac arrest.
What if? If a patient has a tumor of the adrenal medulla (pheochromocytoma), it would lead to excessive production of epinephrine and norepinephrine, causing severe hypertension, palpitations, and headaches. This highlights the potent effects of amino acid-derived hormones.

How to Approach the Question

First, identify the key concept in the question stem, which is 'modified amino acid' hormone.
Recall the three major chemical classifications of hormones: amino acid-derived, peptide/protein, and steroid (lipid-derived).
Systematically evaluate each option to determine its chemical class.
Recognize that Estrogen and Progesterone are classic examples of steroid hormones derived from cholesterol.
Identify Prostaglandin as a lipid-derived eicosanoid, distinct from steroids and amino acid derivatives.
Conclude that Epinephrine (adrenaline) is the correct answer, as it is a well-known catecholamine synthesized from the amino acid tyrosine.

Concept Tested & Keywords

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E6 Harper's Illustrated Biochemistry2023 (pp 26-793 of 813) p. 476-478

E6 Physiology Guyton 4SAE Part 3 p. 40-42

E6 Obstetrics Williams p. 3-10

Practise the full HPSSC - 2015

Attempt every question from this paper in a timed mock, then review the full solution for each one.