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Sample

  1. The Patient’s plasma is needed. 
    1. Place blood immediately in ice water and freeze plasma in 15 min.
  2. The sample should be collected in a prechilled plastic test tube with EDTA or heparin.
  3. For the diagnosis of Cushing syndrome, the sample should be taken between 6 to 11 pm.
  4. Centrifuge the sample at 4 °C and store at -20 °C immediately within 15 minutes of collection.

Precaution

  1. A stressful collection of the blood will raise the level.
  2. Avoid physical activity 10 to 12 hours prior to taking the sample.
  3. Stop medication like corticosteroids 48 hours before this test.
  4. Collect the sample in a chilled plastic vial with EDTA or Heparin.
  5. ACTH is very labile and requires antiprotease in the collecting vial.
  6. In the routine, ACTH level is not measured because it degrades in the plasma.
  7. Put the patient on a low carbohydrate diet.

Purpose of the test

  1. This hormone is estimated in various conditions like Adrenal insufficiency, in Cushing syndrome and Acromegaly etc.
  2. In Addison’s disease is >1000 pg /ml
  3. Its level decreases in Secondary Adrenocortical Insufficiency, Adrenal carcinoma, and adenoma.

Pathophysiology

  1. Adrenocortical hormone (ACTH) is produced by the anterior pituitary lobe.

  1. Corticotropin-releasing-hormone (CRH) released from the hypothalamus and give rise to release of ACTH from the pituitary glands.
  2. ACTH is released in response to many stresses.
  3. Now ACTH sends signals to the adrenal gland which secretes steroids (cortisol, androgen, and aldosterone).                                                                                                             

  1. ACTH is 39 amino acid peptide hormone secreted by the anterior pituitary gland.
  2. There are two peaks:
    1. Highest between 6 to 8 AM.
    2. The lowest level between 9 to 10 PM.
    3. During sleep is the normal level.
  3. Pregnancy, menstrual cycle and stress increase the secretion.
  4. ACTH is unstable in the blood. Most commercial RIA kits are insensitive and nonspecific to measure ACTH.
  5. ACTH is advised for investigating disorders of the hypothalamic, pituitary and renal system.
  6. ACTH is secreted by the anterior pituitary gland that signals the adrenal gland to produce steroids ( androgens, cortisol, and aldosterone). These are needed for the normal functioning of the body.
  7. ACTH is released in a burst so its level can vary from minute to minute.
  8. With adrenal insufficiency, the pituitary gland release proopiomelanocortin and ACTH are increased.

Normal ACTH

Cushing’s Syndrome

  1. This may be a form of Hyperadrenalism or Hypercortisolism with common clinical presentations.
  2. The abnormal Overnight Dexamethasone suppression test and 24 hours urinary cortisol test are diagnostic of Cushing’s Syndrome.
  3. When Cushing’s syndrome is due to Pituitary or ectopic source then ACTH levelly is high.
  4. When the source is the Adrenal gland, the ACTH is low.

Table for differentiation of Cushing’s syndrome and Addison’s disease

Disease  ACTH value Cortisol value
Cushing’ syndrome Increased/low  Increased
Adrenal adenoma Low Raised
Adrenal cancer low Raised
ACTH- producing Pituitary tumor Raised Raised
Ectopic ACTH (Lung cancer) Raised Raised
Addison disease    
Adrenal gland failure ( Infarction, Haemorrhage) Raised Low
Congenital adrenal hyperplasia Raised Low
Hypopituitarism Low Low

Increased ACTH level is seen in:

  1. Addison disease (primary adrenal insufficiency).
  2. Ectopic ACTH syndrome.
  3. Cushing’s syndrome. This is dependent upon the adrenal hyperplasia due to the pituitary gland.
  4. Stress.

Decreased ACTH level is seen in:

  1. Hypopituitarism.
  2. Secondary adrenal insufficiency, this is due to pituitary insufficiency.
  3. Adrenal adenoma or cancer.
  4. Exogenous steroid administration.

Test value for the Layman:

  1. This test is advised if the patient has diabetes mellitus, reduced glucose tolerance, and muscle wasting to rule out Cushing syndrome.
  2. If there are truncal obesity and thin extremity.
  3. In case of abnormal lipid metabolism.

Possible References Used

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