Adrenocorticotropic hormone (ACTH) plays a large role in how your body responds to stress. ACTH is produced in the pituitary gland, its production stimulates the production and release of cortisol from the adrenal gland.
After ACTH is made in the pituitary gland, ACTH is released into the bloodstream and travels around the body. Production of ACTH is regulated by corticotrophin-releasing hormone (CRH) from the hypothalamus and cortisol from the adrenal gland. If ACTH levels are low, the hypothalamus releases CRH which is key to the stress hormone system and acts on many areas of the brain such as appetite and memory. Once the CRH is discharged, it triggers the pituitary gland to secrete ACTH.
High levels of ACTH are detected by the adrenal gland, which starts the production of cortisol. When cortisol levels rise in the body, the brain can sense these high levels and the production of the CRH and ACTH decreases.
Stress activates ACTH production and increases cortisol levels.
If too much ACTH is produced, this can lead to high levels of cortisol in the body, also known as Cushing syndrome. The most common cause of increased ACTH production is a benign pituitary tumor. When this is present, the disorder is called Cushing disease. Other endocrine conditions that may lead to an increase of ACTH include adrenal insufficiency and congenital adrenal hyperplasia.
Having lower than normal ACTH levels in the blood can be a result of other endocrine conditions such as Cushing syndrome or hypopituitarism.
To diagnose these conditions, healthcare providers can order an ACTH blood test. An ACTH test is ordered if a cortisol blood test has abnormal results or if a patient has symptoms of too much or too little cortisol. Analyzing ACTH and cortisol levels together can help identify the different endocrine conditions associated with high and low cortisol levels.
To test ACTH levels, healthcare providers may require you to fast overnight and conduct the test early in the morning. This is because ACTH levels are high in the morning and gradually decrease during the day. ACTH is at its lowest level during sleep.
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