Hormones made of many amino acids are classified as peptide hormones.
Peptide hormones are a class of hormones that are composed of chains of amino acids. The length of these chains can vary; some peptide hormones are relatively small, consisting of just a few amino acids (oligopeptides), while others are larger, consisting of many amino acids (polypeptides).
Examples of peptide hormones include:
- Antidiuretic hormone (ADH) or Vasopressin: A short polypeptide hormone produced in the brain and released by the posterior pituitary gland. It helps regulate water balance in the body.
- Oxytocin: Another polypeptide hormone produced in the brain and released by the posterior pituitary gland. It plays a role in social bonding, reproduction, and childbirth.
- Insulin: A larger polypeptide hormone produced by the pancreas. It regulates blood sugar levels.
- Growth hormone: A large polypeptide hormone produced by the anterior pituitary gland. It stimulates growth and cell reproduction.
Peptide hormones, because of their structure, generally cannot pass through the cell membrane. They bind to receptors on the cell surface, which then triggers a cascade of events within the cell, ultimately leading to a change in cellular activity. This mechanism of action differs from steroid hormones, which can pass through the cell membrane and bind to receptors inside the cell.
