Description

ACTH stands for Adrenocorticotropic Hormone, also known as corticotropin. It’s a hormone produced by the anterior pituitary gland, a pea-sized gland located at the base of the brain. Here’s some key information about ACTH:

1. Function: ACTH plays a crucial role in regulating the production and release of cortisol, a steroid hormone, from the adrenal glands. Cortisol is involved in various physiological processes, including metabolism, immune response, and stress regulation. ACTH stimulates the adrenal glands to produce cortisol in response to stress and other stimuli.
2. Regulation: The secretion of ACTH is regulated by the hypothalamus-pituitary-adrenal (HPA) axis, a complex feedback system involving the hypothalamus, pituitary gland, and adrenal glands. The hypothalamus releases corticotropin-releasing hormone (CRH), which stimulates the anterior pituitary gland to release ACTH. ACTH, in turn, stimulates the adrenal glands to produce cortisol. Elevated cortisol levels inhibit the release of both CRH and ACTH through negative feedback mechanisms.
3. Stress Response: ACTH secretion is particularly responsive to stress. In response to stressors such as physical injury, infection, or emotional distress, the HPA axis is activated, leading to increased secretion of ACTH and cortisol. This helps the body cope with the stressor by mobilizing energy reserves, suppressing inflammation, and maintaining blood pressure.
4. Diurnal Variation: ACTH levels typically exhibit a diurnal variation, with higher levels in the early morning and lower levels in the evening and at night. This pattern is influenced by the body’s circadian rhythm and cortisol secretion.
5. Clinical Importance: Abnormalities in ACTH levels or function can lead to various health conditions. For example, excessive ACTH production can result in conditions such as Cushing’s disease, characterized by excess cortisol production and its associated symptoms. Insufficient ACTH production can lead to adrenal insufficiency, where the adrenal glands fail to produce adequate cortisol, causing symptoms such as fatigue, weight loss, and low blood pressure.

Measuring ACTH levels in blood or urine, along with other diagnostic tests, can help diagnose and manage disorders of the adrenal glands and HPA axis. Additionally, ACTH stimulation tests are sometimes performed to assess adrenal function and responsiveness.