What hormones are considered amino acid derivatives?

Amino acid derivatives are hormones that are synthesized from single amino acids. Among the choices provided, epinephrine is correctly classified as an amino acid derivative because it is derived from the amino acid tyrosine. This means that its structure and function are based on variations of amino acids, specifically in how they are modified to create biologically active compounds.

On the other hand, insulin, while crucial for glucose metabolism, is a peptide hormone formed from a chain of amino acids rather than a single amino acid or derivative. Testosterone belongs to the category of steroid hormones, which are lipid-based and synthesized from cholesterol, not from amino acids. Therefore, epinephrine stands out as the sole correct answer that fits the classification of amino acid derivatives in the context of hormones.