A peptide hormone is :

Options

A. Estrogen
B. Testosterone
C. Insulin
D. Corticoid

Explanation

### Step-by-Step Solution

1. **Understanding Peptide Hormones**:
- Peptide hormones are hormones that consist of amino acids linked together by peptide bonds. These bonds are formed through a dehydration reaction where the amino group of one amino acid reacts with the carboxyl group of another, releasing a molecule of water.

2. **Identifying the Structure of Amino Acids**:
- Each amino acid has a central carbon atom, an amino group (-NH2), a carboxyl group (-COOH), and a variable R-side chain. When two amino acids bond, they form a dipeptide, and the bond between them is called a peptide bond.

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