ACTH Test

ACTH also known as adrenocorticotropic hormone is a hormone produced by the pituitary gland. This hormone in turn regulates the production of another important hormone cortisol, made by adrenal glands. Cortisol, known as a 'stress hormone', controls varied reactions in our body that take place in response to stress. Cortisol regulates blood pressure and blood sugar levels in the body and helps in maintaining immune function and anti-inflammatory processes. ACTH travels through the bloodstream to the adrenal glands and stimulates the adrenals to release cortisol. An ACTH blood test is done to measure the level of the adrenocorticotropic hormone in the blood.

Too much or too little ACTH level reveals problems related to adrenal glands or pituitary glands. High level of ACTH points to problems with adrenal glands and low level of ACTH may imply defective pituitary glands. The results of ACTH test is extremely useful in diagnosing Cushing syndrome and adrenal insufficiency.

Higher values of ACTH test are associated with one of the following conditions:

• Addison's disease
  
  
• Adrenal Hyperplasia
  
  
• Cushing's disease
  
  
• Tumor in the adrenal glands or pituitary glands
  
  
• Ectopic ACTH, which means ACTH made by a tumor outside the pituitary gland

Lower levels of ACTH could mean adrenal tumor, Exogenous Cushing syndrome or hypopituitarism, a pituitary dysfunction leading to little or no production of hormone.

Preparing for the test

Patient should not eat or drink for 10 hours prior to the test. It is advisable to take a diet low in carbohydrates for two to three days before the test. Exercise and alcohol should be avoided for 12 hours before the test. Few steroid medications result in low levels of ACTH, hence patient should share all the information regarding the current medication with the doctor. Patient should not have undergone any medical test that uses a radioactive tracer for a week before an ACTH test.

ACTH levels do not remain in the same range through the day. The plasma ACTH levels are highest in the morning and start to decline during the waking hours. Therefore, blood is usually collected in the morning hours or multiple blood samples are sought for accurate diagnosis.

The Normal reference range is as follows:

Morning: Less than 80 pg/mL or less than 18 pmol/L

Evening: Less than 50 pg/mL or less than 11 pmol/L

A significant deviation from the normal range could mean defective adrenal glands or pituitary gland and further investigation is ordered for the accurate diagnosis.