ACTH Stimulation Test: Protocol & Side Effects

Instructor: Danielle Haak

Danielle has a PhD in Natural Resource Sciences and a MSc in Biological Sciences

The field of medicine is full of acronyms, and it can be confusing to try to keep them all straight. This lesson will explain what ACTH is and what it does. Then we'll talk about the ACTH stimulation test and how it works.

What Is ACTH?

Mark is scheduled to have an ACTH Stimulation test, and he doesn't know what to expect so he's feeling nervous. He isn't quite sure why his doctor insisted on this test, so he calls his friend Kelly to ask her a few questions. Kelly is finishing up her last year of medical school and knows more of the details to help calm Mark's nerves. When Mark hangs up the phone, he understands what the ACTH procedure will involve and he's not nervous anymore. What did Kelly say to him?

Well, first, Kelly explained what ACTH is. ACTH is short for adrenocorticotropic hormone and it is a hormone produced by the pituitary gland in the brain. When ACTH is in the blood, it signals the adrenal glands to produce two hormones: cortisol and adrenaline, both of which are related to the body being stressed.

Specifically, cortisol has the potential to affect circulation, the immune system, the nervous system, and metabolism, while adrenaline helps the nervous and circulatory systems function properly. As you can tell, both are pretty important for maintaining normal body function.

What Is an ACTH Stimulation Test?

There are a number of conditions that can occur if the pituitary or adrenal glands aren't working properly. For example, Addison's disease occurs when the adrenal glands don't produce enough cortisol, and hypopituitarism occurs when the pituitary gland doesn't make enough ACTH (meaning the adrenal glands don't receive a signal to produce cortisol or adrenaline).

If it's suspected the adrenal or pituitary glands aren't functioning properly, a physician may perform an ACTH stimulation test. This is a relatively straightforward procedure with minimal side effects. As the name suggests, the test is meant to stimulate the effects of ACTH in the blood, prompting the adrenal glands to release cortisol and adrenaline.

Before the test, a patient may be required to fast (refrain from eating) for the preceding 8 hours. If they are taking certain medications that affect the level of cortisol in the blood, they may have to stop taking them during the 24 hours leading up to the test.

On the day of the test, the first step is to draw a blood sample. This blood will be analyzed for cortisol and the results act as the baseline levels of cortisol in the body during fasting. Then the patient will receive an injection (shot) of a synthetic (man-made) version of ACTH, called cosyntropin. After one hour, another blood sample will be drawn, and the cortisol levels will be re-analyzed.

Cortisol is measured in the blood twice during the ACTH stimulation test.

What Do the Test Results Mean?

When the synthetic ACTH is injected into the blood, it should prompt the adrenal glands to produce and release cortisol and adrenaline. Normal cortisol levels in the blood from the second sample should be higher than 18-20 micrograms per deciliter (mcg/dL). If the cortisol levels are lower than this, it can signal problems with the adrenal or pituitary glands.

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