ACTH stimulation test

Overview

The ACTH stimulation test is a medical test that checks how well your adrenal glands (small glands on top of your kidneys) are working. It measures how your body responds to a hormone called ACTH, which tells your adrenal glands to make cortisol (a stress hormone). This test helps doctors find out if your adrenal glands are not making enough cortisol, a condition called adrenal insufficiency.

This test is not done every day, but it is a standard and widely used test when a doctor suspects adrenal problems. It is considered a key diagnostic tool in endocrinology (the study of hormones).

The test can be performed on people of any age, from infants to older adults. It is most often used for people who have symptoms that suggest their adrenal glands are not working properly.

Symptoms

Common symptoms

• Extreme tiredness that does not get better with rest
• Unintended weight loss
• Low blood pressure (feeling dizzy or fainting when standing up)
• Darkening of the skin (especially in skin creases, scars, or gums)
• Nausea, vomiting, or diarrhea
• Salt craving
• Muscle or joint pain

Symptoms in children

• Poor growth or weight gain
• Frequent vomiting or dehydration
• Unusual skin darkening
• Fatigue that affects school or play
• Low blood sugar (hypoglycemia) – shakiness, confusion, or sweating

Symptoms in older adults

• Confusion or memory problems
• Weakness and falls
• Weight loss with loss of appetite
• Low blood pressure that causes dizziness or fainting
• Infections that are slow to heal

Causes

Main causes

• The adrenal glands are damaged by the body's own immune system (autoimmune Addison’s disease)
• Infections that harm the adrenal glands (like tuberculosis or fungal infections)
• Tumors or bleeding in the adrenal glands (rare)
• Problems with the pituitary gland (a gland in the brain) that makes ACTH
• Long-term use of steroid medications that suppress the adrenal glands

Risk factors

• Having an autoimmune condition (like type 1 diabetes, thyroid disease, or vitiligo)
• Long-term use of corticosteroid medicines for asthma, arthritis, or other conditions
• Family history of adrenal insufficiency
• Infections that affect the adrenal glands (more common in certain parts of the world)

When to see a doctor

See a doctor urgently if:

• If you have symptoms of an adrenal crisis (see emergency symptoms above)
• If you are already on steroid treatment and become very ill or injured (you may need extra medication)

Book a routine appointment if:

• If you have ongoing symptoms like fatigue, weight loss, skin darkening, or low blood pressure that worry you
• If you have been using steroid medicines and are concerned about adrenal function
• If you have a condition that increases your risk for adrenal problems

Diagnosis

The ACTH stimulation test is the main test used to diagnose adrenal insufficiency. It is usually done when blood tests show low cortisol levels or when you have symptoms of the condition.

Tests that may be done

• ACTH stimulation test (also called a cosyntropin test or Synacthen test) – a blood sample is taken before and after an injection of synthetic ACTH
• Blood cortisol and ACTH levels measured at different times
• Other blood tests for electrolytes (sodium and potassium), renin, and aldosterone
• Imaging tests like a CT scan of the adrenal glands if needed

What to expect at your appointment

The test is usually done in the morning. You will have a small needle placed in a vein to collect a blood sample. Then you will get an injection of synthetic ACTH (a harmless substance that mimics the natural hormone). After 30 and/or 60 minutes, another blood sample is taken. The whole process takes about an hour. You may feel a brief pinch from the needle, but it is not painful. After the test you can go home and resume normal activities. Your doctor will discuss the results with you at a follow-up visit.

Treatment

If the ACTH stimulation test shows adrenal insufficiency, treatment focuses on replacing the missing hormones (cortisol and sometimes aldosterone). This is usually lifelong. The goal is to restore hormone levels so your body functions normally.

Self-care at home

• Always carry a medical alert card or bracelet that states you have adrenal insufficiency
• Learn to recognize signs of an adrenal crisis and how to act quickly
• Keep an emergency injection kit (if prescribed by your doctor) and know how to use it
• Stay in regular contact with your healthcare team and do not skip follow-up visits

Medical treatments

Treatment involves taking replacement hormones that mimic what your adrenal glands would normally produce. The main hormone replaced is a type of cortisol. The dose is adjusted based on your body size, activity level, and stress. During illness, injury, or surgery, the dose may need to be increased (called stress dosing). Your doctor will teach you how to adjust your medication. You should never change your medication dose without medical advice.

When is surgery considered?

If you have adrenal insufficiency, any surgery requires careful management of your hormone replacement. Your doctor will give you instructions on how to take extra medication before and after surgery to prevent an adrenal crisis. Always tell your surgeon and anesthesiologist about your condition.

Living with this condition

Living with adrenal insufficiency means taking your hormone replacement every day and being aware of your body's needs. Most people feel normal with proper treatment. You need to plan for sick days, travel, and stressful events by adjusting your medication as advised by your doctor.

Lifestyle tips

• Wear a medical alert bracelet or carry a card that states your condition and medication
• Have an emergency plan for illness or accidents (know when to give extra medication and when to call for help)
• Avoid excessive stress when possible, but learn to manage it
• Travel with extra medication and a copy of your prescription

Diet and exercise

Maintain a healthy diet with adequate salt, especially if you have aldosterone deficiency. Stay well hydrated. Exercise is generally safe, but listen to your body – if you feel very tired or dizzy, stop and rest. Your doctor may recommend adjusting your medication on days you exercise heavily.

Mental health and emotional wellbeing

Living with a chronic condition like adrenal insufficiency can be challenging and may cause anxiety, especially about the risk of a crisis. It is normal to feel worried or stressed. Talking to a mental health professional or joining a support group can help. Remember that with proper care, you can still enjoy a full and active life.

Prevention

Most cases of adrenal insufficiency cannot be prevented because they are caused by autoimmune conditions or other problems that are not under your control. However, you can prevent adrenal crises by carefully managing your medication and knowing how to respond to illness or stress. If you take long-term steroid medicines, your doctor may slowly reduce your dose to minimize the risk of adrenal suppression.

Vaccines

Stay up to date with recommended vaccines, including the flu and pneumonia vaccines, to reduce your risk of infections that could trigger an adrenal crisis. Talk to your doctor about which vaccines are right for you.

Screening programmes

Routine screening for adrenal insufficiency is not recommended for the general public. However, if you have a condition that increases your risk (like an autoimmune disease or long-term steroid use), your doctor may do blood tests to check your cortisol levels. The ACTH stimulation test is used when initial tests suggest a problem.

Complications

If left untreated

• Adrenal crisis – a life-threatening emergency with severe vomiting, low blood pressure, and loss of consciousness
• Chronic fatigue and weakness that limit daily activities
• Weight loss and malnutrition
• Low blood sugar (hypoglycemia) leading to confusion or seizures
• Increased risk of infections due to poor immune function

Long-term outlook

With early diagnosis and proper treatment, the outlook for adrenal insufficiency is very good. Most people lead normal, active lives and have a normal life expectancy. The key is to take your medication as prescribed, learn to manage stress and illness, and maintain regular follow-up with your healthcare team. Adrenal crises can be prevented with good self-care and awareness. While the condition is lifelong, it does not have to stop you from enjoying your life.

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