Final answer:
Exocytosis of hormone-filled vesicles requires calcium ions.
Step-by-step explanation:
The exocytosis of hormone-filled vesicles requires calcium ions. Calcium ions play a crucial role in the fusion of the vesicles with the plasma membrane, allowing the release of their contents into the cell's exterior. This process is essential for hormone secretion and cell communication. Examples of hormones that utilize calcium ions as a second messenger system include angiotensin II and growth hormone-releasing hormone (GHRH).