Which system is regulated by hormones secreted by the pituitary gland?

The endocrine system is the correct answer because it is primarily governed by hormones, many of which are secreted by the pituitary gland, often referred to as the "master gland." The pituitary gland plays a crucial role in regulating various hormonal functions within the body, influencing growth, metabolism, and reproductive processes.

The hormones released by the pituitary gland affect other endocrine glands, such as the thyroid gland, adrenal glands, and gonads. This intricate system of hormone regulation is vital for maintaining homeostasis and addressing various physiological needs.

In contrast, the respiratory, circulatory, and digestive systems primarily involve the mechanical and biochemical processes of breathing, blood circulation, and food breakdown, respectively, rather than being directly regulated by hormones from the pituitary gland. While hormones from the endocrine system can influence these systems, the direct regulatory role of the pituitary gland specifically aligns with the functions of the endocrine system.