Summary

• ACTH or adrenocorticotropic hormone helps regulate cortisol and male sex hormones in your body.  
• Although widely known as the stress hormone, cortisol is needed in many of your body’s vital processes. 
• Normally, ACTH rises when cortisol is low and falls when cortisol is high. 
• If you make too much or too little cortisol, testing ACTH and cortisol at the same time can help to show if you have a problem in your pituitary gland, adrenal glands or elsewhere in the body.

What is ACTH and how does it control cortisol?

Cortisol is a steroid hormone that is involved in many different functions throughout the body. It is best known for priming your body to respond to stress – the fight or flight response. It also helps control your body’s use of food such as fats, proteins and carbohydrates, helps stop inflammation, regulates blood glucose and keeps blood pressure stable. It also has a role in stimulating sex hormones.

Cortisol levels follow a daily pattern, rising in the early morning, peaking at about 8 a.m., and falling in the evening. This is known as the diurnal rhythm. Infections, trauma, exercise, obesity and even being hot or cold influence the amount of cortisol made by your body and can disrupt this diurnal rhythm. 

Your ACTH and cortisol levels are controlled by a complex feedback system of hormones. Hormones are your body’s chemical messages that are sent out from various glands to affect the way your body works.

• The amount of ACTH and cortisol you make is regulated by the hypothalamus, a cluster of cells located deep within your brain and responsible for keeping your body’s nervous and endocrine systems in balance. Your endocrine system controls many of your body’s basic functions such as mood, growth and repair.
• The hypothalamus sends chemical messages to the pituitary, a small gland at the base of the brain. The pituitary then releases ACTH into your bloodstream.
• Cortisol is made by the adrenals, small glands that sit on top of each of your two kidneys.
• When levels of cortisol fall the hypothalamus sends signals to the pituitary to produce more ACTH and this tells the adrenal glands to produce cortisol, and when cortisol levels are too high the opposite happens.
• For the right amount of cortisol to be made, the hypothalamus, the pituitary and the adrenal glands must all be working together. 

Why get tested?

ACTH is usually requested to help diagnose Cushing's syndrome (including Cushing’s disease), tumours of the pituitary and adrenal glands, tumours in other parts of the body and Addison's disease. These are all rare conditions.

Cushing’s syndrome

Cushing’s syndrome is caused when your body makes too much cortisol. It can cause many symptoms including weight gain and thinning skin. Your body can make too much cortisol for many reasons including:

• a tumour in the pituitary or adrenal glands,  
• an overgrowth of the adrenal glands called adrenal nodule hyperplasia,
• a tumour somewhere else in the body producing too much ACTH, or
• taking steroid medications for a long time, such as when you have an autoimmune disease.

When Cushing’s Syndrome is due to a tumour, the tumours are usually benign (not cancer).

Cushing’s disease

Cushing’s disease is a type of Cushing’s syndrome. It is caused when there is a benign (non-cancerous) tumour in your pituitary gland which causes the pituitary gland to make too much ACTH. This extra ACTH stimulates your body to make more cortisol than it should. It is responsible for about eight out of 10 cases of Cushing’s syndrome.

Ectopic ACTH syndrome

Ectopic ACTH syndrome is when you have high ACTH levels because you have a tumour elsewhere in your body, such as in the lungs, pancreas or thyroid. The most common type is small cell lung cancer. Ectopic ACTH syndrome is rare.

Primary adrenal insufficiency – Addison’s disease

In Addison's disease, which is called primary adrenal insufficiency, you have high levels of ACTH and low levels of cortisol. It is due to damage to the adrenal gland which makes cortisol. This damage is often due to an autoimmune disease.

Secondary adrenal insufficiency

In secondary adrenal insufficiency you have high levels of ACTH and low levels of cortisol because of a problem with your pituitary gland. As a result, your pituitary gland doesn’t release enough ACTH to make your adrenal glands produce cortisol.

Congenital Adrenal Hyperplasia (CAH)

CAH is a group of inherited disorders that affect the adrenal glands. Children with CAH usually make too much male sex hormones and not enough cortisol and aldosterone. ACTH is measured in children suspected of having CAH.

Hypopituitarism

Hypopituitarism is a rare condition in which the pituitary gland does not make enough ACTH and cortisol. It is usually due to a benign tumour that affects the production of these hormones. As the tumour grows, it can press on and damage tissue. This disrupts the pituitary gland's ability to make hormones.

Having the test

Sample

Blood.

Any preparation?

Some drugs can cause ACTH levels to rise, including amphetamines, insulin, levodopa and metoclopramide. It is important that you talk with your doctor about any medications you are taking.

In Cushing’s syndrome the diurnal rhythm pattern is usually lost, so measuring late night blood or saliva cortisol is often used if your medical team suspects this diagnosis.  

If your medical team wants to make sure that your high levels of cortisol are not just the result of your body being stressed, you may be asked to take a dexamethasone pill the night before having a cortisol test.  Dexamethasone acts like cortisol and switches off ACTH production. It helps differentiate between Cushing’s syndrome and stress.

A low morning blood cortisol level does not necessarily mean you have Addison’s disease and a Synacthen stimulation test is often needed to make this diagnosis. Synacthen is a synthetic form of ACTH that stimulates the adrenal gland to produce cortisol.

Your results

Reading your test report

Your results will be presented along with those of your other tests on the same form.  You will see separate columns or lines for each of these tests.

Questions to ask your doctor

The choice of tests your doctor makes will be based on your medical history and symptoms. It is important that you tell them everything you think might help.

You play a central role in making sure your test results are accurate. Do everything you can to make sure the information you provide is correct and follow instructions closely.

Talk to your doctor about any medications you are taking. Find out if you need to fast or stop any particular foods or supplements. These may affect your results. Ask:

• Why does this test need to be done?
• Do I need to prepare (such as fast or avoid medications) for the sample collection?
• Will an abnormal result mean I need further tests?
• How could it change the course of my care?
• What will happen next, after the test?

More information

Pathology and diagnostic imaging reports can be added to your My Health Record.

You and your healthcare provider can now access your results whenever and wherever needed. Get further trustworthy health information and advice from healthdirect.