The endocrine system plays a crucial role in regulating various physiological processes through the release of hormones. One such hormone is cortisol, produced by the adrenal cortex. Cortisol is often referred to as the 'stress hormone' because its levels increase in response to stressors. Chronic elevation of cortisol can lead to several physiological effects, including alterations in glucose metabolism, immune response suppression, and even effects on mood and behavior. Understanding the pathway of cortisol release and its effects on the body can help in recognizing disorders related to the endocrine system.

Which of the following glands primarily stimulates the adrenal cortex to release cortisol?