Adrenocorticotropic Hormone
(ACTH)

Sample type: -

Plasma (EDTA), frozen

Uses: -

Diagnosis of Addison disease, CAH, Cushing syndrome, adrenal carcinoma, and ectopic ACTH syndrome.

Precautions: -

• ACTH should be drawn between 7 AM and 10 AM.

Interfere action: -

1. Plasma levels of ACTH exhibit a significant diurnal variation. ACTH is normally highest in the early morning (6–8 AM) and lowest in the evening (6–11 PM). Cortisol levels are frequently measured at the same time as ACTH.

2. Because ACTH is released in bursts, its levels in the blood can vary from minute to minute.

3. ACTH is unstable in blood, and proper handling of specimen is important.

4. Most commercial RIAs are insensitive and nonspecific, measuring intact ACTH as well as precursors and fragments. Highly sensitive IRMAs measure intact ACTH only.

5. RIAs are recommended for investigating ectopic ACTH–producing tumors, because some of the tumors secrete ACTH precursors and fragments. IRMAs are more sensitive than RIAs and are useful for investigating disorders of the hypothalamic–pituitary–adrenal system.

6. Patients taking glucocorticoids may have suppressed levels of ACTH with an apparent high level of cortisol.

7. Pregnancy, menstruation, and stress increase secretion.

Pre analytical error: -

• Thawed specimen; serum or heparinized plasma specimen; specimen collected in no siliconized glass tube.

Corrective action: -

• Should be careful on the tube color.

Post analytical error: -

• Wrong result was sent.

Corrective action: -

• If the result is still not delivered, ask to repeat the test, and apologize for the patient.

Reference range: -

• <46 pg/mL.

• 7.2−63.3 pg/mL, for samples collected between 7 AM and 10 AM.