What is an ACTH test?
Adrenocorticotropic hormone (ACTH) is a hormone produced in the anterior, or front, pituitary gland in the brain. The function of ACTH is to regulate levels of the steroid hormone cortisol, which released from the adrenal gland.
ACTH is also known as:
- adrenocorticotropic hormone
- serum adrenocorticotropic hormone
- highly-sensitive ACTH
- cosyntropin, which is a drug form of ACTH
An ACTH test measures the levels of both ACTH and cortisol in the blood and helps your doctor detect diseases that are associated with too much or too little cortisol in the body. Possible causes of these diseases include:
- a pituitary or adrenal malfunction
- a pituitary tumor
- an adrenal tumor
- a lung tumor
How the ACTH test is performed
Your doctor may advise you not to take any steroid drugs before your test. These can affect the accuracy of the results.
The test is usually done first thing in the morning. ACTH levels are highest when you’ve just woken up. Your doctor will likely schedule your test for very early in the morning.
ACTH levels are tested using a blood sample. A blood sample is taken by drawing blood from a vein, usually from the inside of the elbow. Giving a blood sample involves the following steps:
- A healthcare provider first cleans the site with an antiseptic to kill germs.
- Then, they’ll wrap an elastic band around your arm. This causes the vein to swell with blood.
- They’ll gently insert a needle syringe into your vein and collect your blood in the syringe tube.
- When the tube is full, the needle is removed. The elastic band is then removed, and the puncture site is covered with sterile gauze to stop the bleeding.
Why the ACTH test is performed
Your doctor may order an ACTH blood test if you have symptoms of too much or too little cortisol. These symptoms can vary widely from person to person and are often a sign of additional health problems.
If you have a high cortisol level, you may have:
- a rounded face
- fragile, thin skin
- purple lines on the abdomen
- weak muscles
- an increased amount of body hair
- high blood pressure
- low potassium levels
- high bicarbonate level
- high glucose levels
The symptoms of low cortisol include:
- weak muscles
- weight loss
- increased skin pigmentation in areas not exposed to the sun
- a loss of appetite
- low blood pressure
- low blood glucose levels
- low sodium levels
- high potassium levels
- high calcium levels
Risks of an ACTH test
Blood tests are normally well-tolerated. Some people have smaller or larger veins, which may make taking a blood sample more difficult. However, risks associated with blood tests like the ACTH hormone test are rare.
Uncommon risks of having blood drawn include:
- excessive bleeding
- lightheadedness or fainting
- hematoma, or blood pooling under the skin
- infection at the site
What to expect after an ACTH test
Diagnosing ACTH diseases can be highly complex. Your doctor may need to order more laboratory tests and perform a physical examination before they can make a diagnosis.
For ACTH secreting tumors, surgery is usually indicated. Sometimes, drugs such as cabergoline can be used to normalize cortisol levels. Hypercortisolism due to adrenal tumors usually requires surgery as well.