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Question 495
Endocrinology → General
Classification
Question
SSBAQuestion Header
Which amino acid is the precursor for melatonin synthesis?
Question Stem
Select the single best answer.
Options
A
Tyrosine
B
Phenylalanine
C
Histidine
D
Tryptophan
E
Glycine
Explanation
Melatonin is derived from tryptophan. In contrast, the thyroid hormones and the catecholamines adrenaline, noradrenaline and dopamine are derived from tyrosine.
Option Validity
A) Tyrosine is the precursor identified for thyroid hormones and catecholamines, not melatonin.
B) Phenylalanine is not identified as the direct precursor for melatonin in this classification.
C) Histidine is not the precursor for melatonin.
E) Glycine is not the precursor for melatonin.
Further Reading
Saxena, MRCOG-1 Basic Sciences, Endocrinology: Chemical Structure of Hormones and Pineal Gland, pp. 300 and 304.