Cortisol is primarily regulated by which hormone?

• A. Growth hormone
• B. Adrenocorticotropic hormone (ACTH)
• C. Thyroid stimulating hormone (TSH)
• D. Prolactin

Answer: (B)

Cortisol, a hormone produced by the adrenal cortex, plays a critical role in the body's response to stress, metabolism, and immune function. Its regulation is primarily controlled by adrenocorticotropic hormone (ACTH). ACTH is secreted by the anterior pituitary gland in response to corticotropin-releasing hormone (CRH) from the hypothalamus. When ACTH enters the bloodstream, it stimulates the adrenal glands to produce and release cortisol.

The feedback mechanism involving cortisol is important for maintaining homeostasis. Elevated levels of cortisol signal the hypothalamus and pituitary gland to reduce the secretion of CRH and ACTH, thus preventing excessive cortisol production. This dynamic regulation ensures that cortisol levels remain within a physiological range, responding appropriately to the body's needs.

In contrast, other hormones listed do not have a primary regulatory role over cortisol. Growth hormone, thyroid-stimulating hormone (TSH), and prolactin influence different physiological processes and target glands but do not directly regulate cortisol production. Their focus is on growth, metabolism of thyroid hormones, and lactation, respectively. Thus, the role of ACTH in the regulation of cortisol is well-established and crucial for understanding the endocrine system's functioning.