Step 1: Understanding the Concept:
Hormones are chemically classified as peptides/proteins, steroids, or amino acid derivatives. We need to identify the polypeptide hormone from the list.
Step 3: Detailed Explanation:
Epinephrine (Adrenaline): This is an amino acid derivative (specifically, a catecholamine derived from Tyrosine).
Insulin: This is a peptide hormone produced by beta cells of the pancreas. It consists of 51 amino acids arranged in two chains (A and B) linked by disulfide bridges. Thus, it is a polypeptide.
Estrogen: This is a steroid hormone (lipid-soluble).
Androgen (Testosterone): This is also a steroid hormone.
Step 4: Final Answer:
Insulin is the polypeptide hormone.