Adrenocorticotropic Hormone (ACTH)
What is adrenocorticotropic hormone (ACTH)?
Adrenocorticotropic hormone (ACTH) is a hormone your pituitary gland releases that plays a large role in how your body responds to stress. The release of ACTH triggers your adrenal glands to produce cortisol, the “stress hormone,” and androgens (a group of sex hormones).
Hormones are chemicals that coordinate different functions in your body by carrying messages through your blood to your organs, skin, muscles and other tissues. These signals tell your body what to do and when to do it.
Your pituitary gland is a small, pea-sized gland located at the base of your brain below your hypothalamus. It’s a part of your endocrine system. Your pituitary gland is made of two lobes: the anterior (front) lobe and posterior (back) lobe. Your anterior pituitary lobe makes and releases ACTH.
What is the function of adrenocorticotropic hormone (ACTH)?
The main function of adrenocorticotropic hormone is to stimulate your adrenal glands to release cortisol.
Cortisol is an essential hormone that affects almost every organ and tissue in your body. Cortisol is widely known as the “stress hormone.” However, it has many important effects and functions throughout your body aside from regulating your body’s stress response.
Cortisol’s many important roles include:
- Regulating your body’s stress response.
- Helping control your body’s use of fats, proteins and carbohydrates, or your metabolism.
- Suppressing inflammation.
- Regulating blood pressure.
- Regulating blood sugar.
- Helping control your sleep-wake cycle.
ACTH also plays a role in stimulating your adrenal glands to release androgens (sex hormones) and stimulating the production of chemical substances that stimulate an increase in other hormones such as adrenaline and noradrenaline.
How are ACTH levels controlled?
Your body controls adrenocorticotropic hormone levels in a feedback system that involves your hypothalamus, pituitary gland, adrenal glands and certain hormones. This is called the hypothalamic-pituitary-adrenal (HPA) axis.
Your pituitary gland is connected to your hypothalamus through a stalk of blood vessels and nerves. This is called the pituitary stalk. Through the stalk, your hypothalamus communicates with your pituitary gland and tells it to release certain hormones. Your hypothalamus is the part of your brain that controls functions like blood pressure, heart rate, body temperature and digestion.
Your adrenal glands are small, triangle-shaped glands that are located on top of each of your two kidneys.
The feedback system that controls ACTH levels involves the following steps:
- When cortisol levels are low, your hypothalamus releases corticotrophin-releasing hormone (CRH).
- CRH stimulates your anterior pituitary lobe to release ACTH.
- ACTH then triggers your adrenal glands, specifically your adrenal cortex, to release cortisol and androgens.
- The resulting increase in cortisol then signals your hypothalamus to decrease CRH levels, thus completing the feedback loop.
Stress also stimulates adrenocorticotropic hormone production and the resulting increase in cortisol levels.
If there are any issues with your hypothalamus, pituitary gland or adrenal glands, it can affect the balance of hormones involved in this process, including ACTH.
What test checks ACTH levels?
A blood test can measure adrenocorticotropic hormone levels through a blood sample taken from a vein in your arm.
Healthcare providers often order an ACTH test along with a cortisol test to diagnose issues with your pituitary or adrenal glands.
Healthcare providers may also order an ACTH stimulation test, which measures how well your adrenal glands respond to ACTH, to help diagnose pituitary and/or adrenal gland issues.
What are normal ACTH levels?
Like cortisol, the level of ACTH in your blood normally peaks in the early morning and declines throughout the day, reaching its lowest level around midnight. This pattern can change if you work a night shift and sleep at different times of the day.
Because of this, ACTH tests usually require a morning blood draw. In general, the normal range for ACTH levels is 7.2 to 63.3 picograms per milliliter (pg/mL) from 7:00 a.m. to 10:00 a.m.
Normal ranges can vary from lab to lab, time to time and person to person. If you need to get an ACTH test, your healthcare provider will interpret your results and let you know if you need to get further testing.
What happens when ACTH levels are high?
If you have high levels of adrenocorticotropic hormone, you’ll likely also have high cortisol levels. Since cortisol affects your body in many ways, you’ll experience side effects of high cortisol levels, not necessarily high ACTH levels. In cases where your adrenal glands don’t produce enough cortisol, you may have increased ACTH levels. Again, you’ll experience symptoms related to low cortisol, not high ACTH.
Causes of high adrenocorticotropic hormone levels include:
- Cushing’s disease: This is the most common cause of increased ACTH levels. A benign (non-cancerous) tumor (adenoma) in your pituitary gland that produces excess amounts of ACTH, which then elevates cortisol levels, causes ACTH. It’s important to note the difference between Cushing’s disease and Cushing’s syndrome. The disease is one of the many causes of the syndrome.
- Ectopic adrenocorticotropic hormone tumor: Rarely, a tumor outside of your pituitary gland can release excess ACTH. Tumors that can (but rarely) produce ACTH include benign carcinoid tumors of the lung, islet cell tumors of the pancreas, medullary carcinoma of the thyroid, small cell tumors of the lung and tumors of the thymus gland.
- Primary adrenal insufficiency: This condition happens when your adrenal glands don’t produce enough cortisol due to some type of damage to your adrenal glands. Addison’s disease is the most common cause of primary adrenal insufficiency. As a result, your pituitary gland releases excess ACTH to try to stimulate your adrenal glands.
What happens when ACTH levels are low?
Low adrenocorticotropic hormone levels due to a pituitary gland condition usually cause low cortisol levels, whereas high cortisol levels due to an adrenal gland issue usually cause low ACTH levels.
Causes of low ACTH levels include:
- Cushing’s syndrome: Cushing’s syndrome from an adrenal tumor or by long-term use of corticosteroid medication for other conditions can cause low ACTH levels. This is because the excess cortisol prevents your pituitary gland from releasing regular amounts of ACTH.
- Hypopituitarism: This is a rare condition in which there’s a lack (deficiency) of one, multiple or all of the hormones made by your pituitary gland. ACTH can be one of the affected hormones. Any type of damage to your pituitary gland, such as pressure on the gland, surgical damage or radiation therapy, can cause hypopituitarism.
A note from Cleveland Clinic
Adrenocorticotropic hormone (ACTH) is essential for regulating your cortisol levels. If you’re experiencing symptoms of high or low cortisol levels, such as weight gain or loss and high or low blood pressure, respectively, it’s important to contact your healthcare provider. They may order cortisol and ACTH blood tests to see if your adrenal glands or pituitary gland are responsible for your symptoms.
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