Which of the following is NOT classified as an amino acid-derived hormone?

• A. Thyroid hormones
• B. Histamine
• C. Cortisol
• D. Melatonin

Answer: (C)

Cortisol is classified as a steroid hormone, not an amino acid-derived hormone. Steroid hormones are synthesized from cholesterol and include hormones like cortisol, which is produced by the adrenal cortex. They typically have distinct structures and mechanisms of action compared to amino acid-derived hormones.

In contrast, thyroid hormones, histamine, and melatonin are all derived from amino acids. Thyroid hormones, for example, are formed from tyrosine and are critical in regulating metabolism. Histamine, which plays roles in immune responses and neurotransmission, is derived from the amino acid histidine. Melatonin is synthesized from tryptophan and regulates sleep-wake cycles. Therefore, classifying cortisol as an amino acid-derived hormone is incorrect because it belongs to a completely different category of hormones.