Adrenocorticotropic hormone (ACTH)

Definition

Adrenocorticotropic hormone (ACTH) is a peptide hormone produced by the anterior pituitary gland that stimulates the adrenal cortex to release cortisol and other glucocorticoids. This hormone plays a crucial role in the body's response to stress, influencing metabolism, immune response, and maintaining homeostasis.

5 Must Know Facts For Your Next Test

1. ACTH is secreted in response to stress signals from the hypothalamus through corticotropin-releasing hormone (CRH).
2. Elevated levels of ACTH can lead to increased production of cortisol, which helps manage stress but can have negative effects when chronically elevated.
3. ACTH has a circadian rhythm, meaning its levels fluctuate throughout the day, generally peaking in the early morning.
4. Disorders related to ACTH include Cushing's disease, characterized by excessive ACTH production leading to high cortisol levels.
5. ACTH is also used clinically as a diagnostic tool to assess adrenal function and differentiate between primary and secondary adrenal insufficiency.

Review Questions

• How does ACTH relate to the hypothalamic-pituitary-adrenal (HPA) axis and its role in stress response?
  • ACTH is a key component of the hypothalamic-pituitary-adrenal (HPA) axis, which regulates the body's response to stress. When stress occurs, the hypothalamus releases corticotropin-releasing hormone (CRH), stimulating the anterior pituitary to secrete ACTH. In turn, ACTH prompts the adrenal cortex to produce cortisol, helping the body cope with stressors. This interaction demonstrates how ACTH is crucial in linking neuroendocrine signals with physiological responses.
• Discuss the clinical significance of measuring ACTH levels in diagnosing adrenal disorders.
  • Measuring ACTH levels is vital for diagnosing adrenal disorders because it helps distinguish between primary adrenal insufficiency and secondary causes related to pituitary function. In primary adrenal insufficiency, such as Addison's disease, ACTH levels are elevated due to low cortisol production from the adrenal glands. Conversely, in secondary adrenal insufficiency resulting from pituitary dysfunction, ACTH levels are low. This differentiation is essential for determining appropriate treatment strategies.
• Evaluate how chronic stress affects ACTH and cortisol levels and their implications for overall health.
  • Chronic stress leads to prolonged elevation of ACTH and cortisol levels, disrupting normal hormonal balance and homeostasis. This persistent activation of the HPA axis can result in a range of health issues, including metabolic syndrome, immune suppression, anxiety, depression, and cardiovascular problems. Understanding this relationship underscores the importance of stress management and its impact on long-term health outcomes.

Related terms

Cortisol: Cortisol is a steroid hormone released by the adrenal cortex that helps regulate metabolism, immune responses, and stress responses.

Hypothalamus: The hypothalamus is a brain region that regulates the endocrine system by producing hormones that control the pituitary gland, including corticotropin-releasing hormone (CRH), which stimulates ACTH release.

Pituitary Gland: The pituitary gland is a small gland at the base of the brain known as the 'master gland' because it controls various hormonal functions throughout the body, including the secretion of ACTH.