Introduction

ACTH is produced by the frontal or anterior pituitary gland, located at the base of the brain. It regulates the cortisol hormones’ secretion from the adrenal gland and is required for the body's stress management mechanism. The ACTH test is used to measure the amount of adrenocorticotropic and cortisol hormones in the body that helps identify cortisol abnormalities and disorders.

The normal range of ACTH for an adult falls within 10 to 60 pg/ml at around 8 am. The ACTH levels fluctuate throughout the day depending on factors such as a good night's sleep, pregnancy, mental stress, and intake of insulin or steroidal drugs. A high ACTH level indicates Addison’s disease or tumour formation, while a low level indicates adrenal insufficiency, Cushing’s syndrome, or hypopituitarism.

ACTH test is generally prescribed if you show signs of abnormal cortisol secretion. A few symptoms of higher cortisol secretion include:

• A rotund face
• Obesity
• Purple lineation of the abdomen
• Fragile, papery skin
• High blood pressure
• Reduced blood potassium
• Diabetes
• Unusual body hair growth

Some symptoms of low cortisol secretion are:

• Muscle weakness
• Weight loss 
• Low blood sugar and pressure 
• Weariness

ACTH is a simple blood test. The healthcare professional will wrap a tourniquet around your arm, inject a syringe into a vein on the inside of your elbow, and draw blood, which will be collected in a sterile vial. This takes less than five minutes. However, it may sting slightly. During the ACTH stimulation test, a small shot of synthetically prepared ACTH is injected into the shoulder, and a blood test is performed again.

The ACTH stimulation test is used to detect the adrenal glands’ reaction to the ACTH hormone injection. First, blood is drawn for the ACTH test. Then a shot of 1 mcg to 250 mcg (micrograms) is injected into the shoulder muscle, and after 30 to 60 minutes, blood is collected again. One may feel slight pain or a prick when the injection is administered and a brief throbbing pain after the test is done. The side effects normally include dizziness, palpitations, itching, sweating, and redness.

The normal value of ACTH plasma concentration is between 10 and 60 pg/ml, i.e., from 2.2 to 3.3 pmol/L at 8 am. This level decreases to around 20 pg/ml or 4.5 pmol/L at around 4 pm when the patient stays awake throughout the day. It is even lower, around less than 5pg/mL, i.e., 1.1 pmol/L, within an hour of falling asleep.

A low level of ACTH indicates adrenal insufficiency or hypopituitarism, or Addison’s disease. It may also be caused by a head injury that damages the pituitary gland, surgical procedures, radiation exposure, tumour formation, or stroke. The patient usually suffers from anorexia (loss of appetite), reduced blood sugar and blood pressure, lethargy, irregular menstrual cycle and infertility (in females), frequent urination, and subsequent adrenal crisis, which can be fatal.

It takes less than 5 minutes to collect the blood samples for an ACTH test. The samples are tested in the laboratory using immunoassay methods, and the lab generally takes 2 to 5 days to give accurate results. This test is the easiest way to determine pituitary or adrenal gland malfunction, which may lead to life-threatening conditions.

No, it is generally not. However, patients are advised not to take steroids, OTC drugs, or supplements or perform any radio-isotopic scans 48 hours before the test. Additionally, a diet high in sodium and rich in carbohydrates should usually be avoided 12 hours before the test. In practice, blood samples are collected before 10 am, as the ACTH levels are optimum during this time.

One should avoid high-sodium, carbohydrate-rich foods 48 hours before the ACTH test. Any intake of supplements or steroids should also be avoided. Patients are advised not to drink and eat post-midnight. Along with the points mentioned above, adequate sleep without emotional stress helps prepare better for a morning ACTH test.

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