The adrenocorticotropic hormone (ACTH) is synthesized in the anterior pituitary stimulated by corticotropin releasing hormone (CRH) and hypothalamic feedback inhibited by glucocorticoids (cortisol, cortisone, prednisolone, triamcinolone, dexamethasone).
Its secretion follows a circadian rhythm: up the morning after 6-8 hours of sleep, it decreases in the day to be the lowest around midnight.
• Diagnosis of low adrenal insufficiency suspected in Vespers asthenia, low blood pressure, skin pigmentation.
• Differential diagnosis of Cushing’s syndrome ACTH-dependent distinguishing forms (Cushing’s disease) and ACTH-independent (adrenal tumors).
Sample:
Sampling is done in the morning, between 6 and 8 pm when ACTH secretion is highest. The blood is collected in a special tube, heparin, chilled, and should be sent immediately to the laboratory (ACTH is very fragile).
Typical values:
At 8 am:
<50 pg / mL (10 pmol / L)
Interpretation:
In case of primary adrenal insufficiency (Addison’s disease) in plasma ACTH is still high:> 100 pg / mL (22 pmol / L).
If hypercortisolism:
• ACTH is high and its circadian cycle is abolished, it is Cushing’s disease due to an adenoma of the pituitary or a malignant tumor (lung, pancreatic, gastric) producer of ACTH;
• it is collapsed or undetectable in adrenal tumors. (See Cortisol)