How do protein hormones regulate body functions?

Protein hormones regulate body functions by acting as chemical messengers that target specific tissues to initiate physiological responses. Because they are water-soluble, these hormones travel readily through the blood to reach their destinations.1

The regulation process follows these key steps:

• Binding to Receptors: Unlike steroid hormones, which can penetrate the cell membrane, protein hormones bind to specific receptors located on the surface of target cells.12
• Signal Transduction: Once the hormone binds to its receptor, the hormone-receptor complex triggers a chain of chemical responses within the cell. This process may involve the activation of intracellular enzymes or the stimulation of DNA to promote protein synthesis.1
• Specificity: Because each receptor has a high affinity for a particular hormone, protein hormones only affect tissues that express the corresponding receptor, ensuring that hormonal actions are targeted rather than general throughout the body.1

Ultimately, these actions allow protein hormones to control complex processes, such as stimulating the synthesis of other hormones or regulating metabolic activities within the target cells.13