Final answer:
ACTH, or adrenocorticotropic hormone, is a hormone that stimulates the adrenal cortex to release corticosteroids, including cortisol and aldosterone, which play significant roles in stress response, metabolism, and blood pressure regulation. It is regulated by CRH from the hypothalamus and is part of a negative feedback system that maintains hormonal balance.
Step-by-step explanation:
The adrenocorticotropic hormone (ACTH), also known as corticotropin, is a peptide hormone produced and secreted by the anterior pituitary gland. ACTH plays a crucial role in stimulating the adrenal cortex—the outer part of the adrenal glands—to secrete corticosteroid hormones, including glucocorticoids like cortisol and mineralocorticoids like aldosterone. Cortisol has several important functions, especially in the body's response to stress, including the suppression of the immune system, increasing blood sugar through gluconeogenesis, and aiding in the metabolism of fat, protein, and carbohydrates. Aldosterone helps regulate blood pressure by managing the balance of sodium and potassium in the blood.
ACTH is synthesized from a larger precursor molecule called pro-opiomelanocortin (POMC), which when cleaved, also produces other biologically active molecules such as melanocyte-stimulating hormone and endorphins, the brain's opioid peptides. The secretion of ACTH by the pituitary gland is under the tight control of the corticotropin-releasing hormone (CRH) from the hypothalamus, which itself is influenced by many factors including stress.
In situations of long-term stress, the hypothalamus stimulates the release of ACTH from the pituitary gland, which in turn leads to the release of glucose and fatty acids into the bloodstream, providing the body with necessary energy. The effect of ACTH on the adrenal cortex is an essential aspect of the body's long-term stress response, and the glucocorticoid hormones have potent anti-inflammatory and immune system-suppressing properties.
Negative feedback mechanisms regulate the levels of ACTH and corticosteroids in the blood. When the levels of glucocorticoids rise too high, they signal the hypothalamus and pituitary to reduce the secretion of CRH and ACTH, maintaining hormonal balance.