- The Patient’s plasma is needed.
- Place blood immediately in ice water and freeze plasma in 15 min.
- The sample should be collected in a prechilled plastic test tube with EDTA or heparin.
- For the diagnosis of Cushing syndrome, the sample should be taken between 6 to 11 pm.
- Centrifuge the sample at 4 °C and store at -20 °C immediately within 15 minutes of collection.
- A stressful collection of the blood will raise the level.
- Avoid physical activity 10 to 12 hours prior to taking the sample.
- Stop medication like corticosteroids 48 hours before this test.
- Collect the sample in a chilled plastic vial with EDTA or Heparin.
- ACTH is very labile and requires antiprotease in the collecting vial.
- In the routine, the ACTH level is not measured because it degrades in the plasma.
- Put the patient on a low carbohydrate diet.
Purpose of the test
- This hormone is estimated in various conditions like Adrenal insufficiency, in Cushing syndrome and Acromegaly etc.
- In Addison’s disease is >1000 pg /ml
- Its level decreases in Secondary Adrenocortical Insufficiency, Adrenal carcinoma, and adenoma.
- Adrenocortical hormone (ACTH) is produced by the anterior pituitary lobe.
- Corticotropin-releasing-hormone (CRH) released from the hypothalamus and give rise to release of ACTH from the pituitary glands.
- ACTH is released in response to many stresses.
- Now ACTH sends signals to the adrenal gland which secretes steroids (cortisol, androgen, and aldosterone).
- ACTH is 39 amino acid peptide hormone secreted by the anterior pituitary gland.
- There are two peaks:
- Highest between 6 to 8 AM.
- The lowest level between 9 to 10 PM.
- During sleep is the normal level.
- Pregnancy, menstrual cycle and stress increase the secretion.
- ACTH is unstable in the blood. Most commercial RIA kits are insensitive and nonspecific to measure ACTH.
- ACTH is advised for investigating disorders of the hypothalamic, pituitary and renal system.
- 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.
- ACTH is released in a burst so its level can vary from minute to minute.
- With adrenal insufficiency, the pituitary gland release proopiomelanocortin and ACTH are increased.
- 6 to 8 a.m = < 80 pg / ml or <18 pmol /L (SI units).
- 6 to 11 p.m = < 50 pg /ml or <11 pmol /L (SI units).
- or less than 120 pg/ml
- Another reference gives the following values:
- 8 AM ( unrestricted activity) = <120 pg/mL
- 4 to 8 PM <85 pg/mL
- Cord blood = 50 to 570 pg/mL
- Newborn = 10 to 185 pg/mL
- This may be a form of Hyperadrenalism or Hypercortisolism with common clinical presentations.
- The abnormal Overnight Dexamethasone suppression test and 24 hours urinary cortisol test are diagnostic of Cushing’s Syndrome.
- When Cushing’s syndrome is due to Pituitary or ectopic source then ACTH levelly is high.
- When the source is the Adrenal gland, the ACTH is low.
Table for differentiation of Cushing’s syndrome and Addison’s disease
|| ACTH value
|ACTH- producing Pituitary tumor
|Ectopic ACTH (Lung cancer)
|Adrenal gland failure ( Infarction, Haemorrhage)
|Congenital adrenal hyperplasia
Increased ACTH level is seen in:
- Addison disease (primary adrenal insufficiency).
- Ectopic ACTH syndrome.
- Cushing’s syndrome. This is dependent upon the adrenal hyperplasia due to the pituitary gland.
Decreased ACTH level is seen in:
- Secondary adrenal insufficiency, this is due to pituitary insufficiency.
- Adrenal adenoma or cancer.
- Exogenous steroid administration.
Test value for the Layman:
- This test is advised if the patient has diabetes mellitus, reduced glucose tolerance, and muscle wasting to rule out Cushing syndrome.
- If there are truncal obesity and thin extremity.
- In case of abnormal lipid metabolism.
Possible References Used
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