Final answer:
Peptide hormones and catecholamines are released via exocytosis, whereas steroid hormones and thyroid hormones are released by simple diffusion and then bind to transport proteins in the bloodstream.
Step-by-step explanation:
Hormone Release Mechanisms
The question involves understanding how different types of hormones are released from their parent endocrine cells. The mechanisms of release can be categorized into three main types: exocytosis, transport protein-mediated release, and release via simple diffusion.
- Peptide hormones and catecholamines are typically released from the parent cell via exocytosis. This process involves the hormones being packaged into secretory vesicles which then fuse with the plasma membrane, releasing the hormones into the bloodstream.
- Steroid hormones are lipid-soluble and can diffuse through lipid bilayers of the endocrine cell membranes. Once outside the cell, they bind to transport proteins that keep them soluble in the bloodstream.
- Thyroid hormones, although synthesized by attaching to a protein within the cell, are eventually released into the bloodstream where they mainly circulate bound to transport proteins, which is similar to the mechanism of steroid hormones.
As for the question specifics, peptide hormones and catecholamines are released through exocytosis, while steroid and thyroid hormones, being lipid-soluble, are released from the cell and into the circulation by diffusing through the cell membrane and then binding to transport proteins.