Do you often feel tired, lethargic, or losing weight? When you see a doctor, he or she may decide to check your hormones. Specifically, the hormone cortisol. So, the main test that is done to check if your cortisol levels are normal is the ACTH Stimulation Test. Although the name may sound a bit complicated, it is actually quite simple. Let's talk about it all today.
Simply put, what is this ACTH Stimulation Test?
This is a medical test. To be precise, it looks at how your two organs called adrenal glands respond to a hormone called ACTH (Adrenocorticotropic hormone) that comes from our brain. Does this sound a bit confusing? Okay, let's think about it this way.
Imagine that the pituitary gland in your brain is like the manager of a large company. The two small adrenal glands above your kidneys are like two employees working in that company.
When the manager (pituitary gland) wants to do something, it sends a message called 'ACTH' to the workers (adrenal glands). When this message is received, the workers (adrenal glands) make a hormone called 'cortisol' and release it into the body. This cortisol is a very important hormone for our body. It helps in many things like controlling stress, controlling blood sugar levels, and controlling blood pressure.
So, what the ACTH Stimulation Test does is we inject an externally produced synthetic ACTH hormone (called cosyntropin) into your body and see if your adrenal glands (workers) respond to it and produce cortisol properly.
This test is mainly used to detect a condition called 'adrenal insufficiency' . This means that the adrenal glands are not producing enough cortisol. This is divided into three types.
| Type of adrenal insufficiency | Simply put, what happens? |
|---|---|
| Primary Adrenal Insufficiency | The problem here is with the 'employee'. That is, there is some damage to the adrenal glands . No matter how many messages (ACTH) the manager (pituitary) sends, the employee (adrenal) cannot work. Cortisol is not produced. The best example of this is Addison's disease . |
| Secondary Adrenal Insufficiency | The problem here is with the 'manager'. That is, the pituitary gland is not sending enough messages (ACTH). Even if the worker (adrenal) is fine, he is not working because there is no message. Cortisol is not produced. |
| Tertiary Adrenal Insufficiency | The problem here lies with the 'boss above the manager'. That is, with the part of the brain called the 'hypothalamus'. That is where the message comes from to the manager (pituitary) to work. If that message doesn't come, the manager won't work, and therefore the employee won't work either. |
In what situations does the doctor tell you to do this test?
There may be several reasons why your doctor may recommend this test.
- If a previous blood test showed low cortisol levels: If you have had a blood test for another reason that showed low cortisol levels, you may be asked to do this test to confirm it.
- If you have symptoms of adrenal insufficiency: As we discussed earlier, if you have symptoms such as constant fatigue, weight loss, stomach pain, nausea, dizziness, and low blood pressure, this test is done to find out if this condition is the cause.
- If you have been taking steroids for a long time: When you use glucocorticoid drugs like prednisone for a long time, your pituitary and adrenal glands may temporarily stop working. So, after you stop taking the medication, this test is also done to see if the glands are working properly again.
How should you prepare before the test?
This is very important. You should follow your doctor's instructions exactly. Usually, you can say things like this:
- Fasting: You may be asked not to eat or drink anything for about 6 hours before the test. Only water is allowed.
- Activity restrictions: You may be asked to avoid activities such as strenuous exercise for 12-24 hours before the test.
- Food: Sometimes you may be asked to eat foods that are high in carbohydrates.
- Stopping medication: Some medications you take (especially steroid creams, pills, or inhalers) can affect the test results. Therefore, your doctor may ask you to stop taking them temporarily. Never stop taking your medication without first asking your doctor.
Our body's cortisol levels are not the same throughout the day. They are usually highest in the morning. Therefore, this test is often done in the morning to avoid false results.
Okay, now let's see what happens on the day of the test.
This is not as scary as you might think. It is usually done in a hospital or at the clinic of an endocrinologist. Here is what happens step by step.
1. Taking the first blood sample: First, a nurse will take a blood sample from a vein in your arm. This will check your baseline cortisol level before the test begins.
2. Giving the injection: Next, a nurse will give you an injection containing synthetic ACTH (cosyntropin). This is usually given into the muscle of your arm. It will feel like a small ant stinging you, but it will go away in a few seconds.
3. Second and third blood samples: You will have another blood sample taken 30 minutes after the injection. Then another blood sample will be taken 60 minutes later . This will measure how much cortisol your adrenal glands have produced since the injection.
4. Sending to the laboratory: The blood samples taken are sent to the laboratory.
When you get your blood drawn, you only feel a slight pricking sensation. That goes away after a while. You may feel a small bruise where the blood was drawn, which is normal.
When will the results be available and what will they say?
It can take about a week for the results of this test to come back. This is because once the results are received, your doctor will carefully study them and compare them with your symptoms to come to a conclusion.
What is a normal result?
In a healthy person, after the ACTH injection, the adrenal glands should be well stimulated and the cortisol level in the blood should increase significantly. Your doctor will explain the values in your lab report and the normal range to you.
What is an Abnormal Result?
Remember, your doctor is the best person to explain your test results to you. So don't be afraid to think about the results.
- Primary Adrenal Insufficiency (if there is a problem with the adrenal glands): In a person with this condition, even if an ACTH injection is given, the cortisol level does not increase at all or increases by a very small amount. This is because the problem lies in the adrenal glands, and no matter how much stimulation is given from the outside, they cannot produce cortisol.
- Secondary Adrenal Insufficiency (if there is a problem with the pituitary gland): When the pituitary gland does not release ACTH for a long time, the adrenal glands gradually shrink and begin to become inactive (atrophy). When an ACTH injection is given to such a person, the inactive adrenal glands cannot respond immediately. Therefore, their cortisol levels increase very little or not at all.
Sometimes, if the pituitary gland problem is very recent or only partially affected, cortisol levels may be slightly elevated. Your doctor is the best person to make a decision about all of this.
Take-Home Message
- An ACTH Stimulation Test is a test that looks at how your adrenal glands respond to messages from your brain.
- This is mainly used to diagnose a condition called adrenal insufficiency.
- Follow the doctor's instructions carefully before the test (such as fasting and stopping medication).
- This test involves taking a blood sample, giving an injection, and taking more blood samples.
- Don't worry about the results. Your doctor will interpret them correctly and inform you about the next steps and treatment, if necessary. Don't be afraid to ask your doctor any questions you may have.
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