Which gland is considered the master regulator of endocrine activity?

• A. Pituitary gland
• B. Thyroid
• C. Adrenal
• D. Pineal

Answer: (A)

The central regulator of hormonal activity is the pituitary gland. It releases a group of tropic hormones that tell other endocrine glands when to release their hormones, creating the main channels of communication in the endocrine system. For example, thyroid-stimulating hormone prompts the thyroid to produce thyroid hormones; adrenocorticotropic hormone stimulates the adrenal cortex to release cortisol; follicle-stimulating and luteinizing hormones regulate the gonads; growth hormone influences growth and metabolism. This controlling role is guided by the hypothalamus, which sends releasing or inhibiting signals to the pituitary, forming a hierarchical system where the pituitary coordinates the activity of multiple other glands. The thyroid, adrenal, and pineal glands have important functions too, but they operate downstream of this central control, responding to signals from the pituitary rather than directing the overall endocrine activity.