ACTH (corticotropin) in plasma

Reference interval

• adults (0800 hours): < 120 pg/mL (26 pmol/L)
• adults (1600-2000 hours): < 85 pg/mL (19 pmol/L)
• newborn: 10-185 pg/mL (2.2-41 pmol/L)
• cord blood: 50-570 pg/mL (11-125 pmol/L)
• 9-52 pg/mL (2-11 pmol/L)

Increases

• pharmaceutical agents
  • aminoglutethimide, amphetamines, insulin, L-dopa, metoclopramide, metyrapone, pyrogens, RU 486, vasopressin
• clinical disorders:
  • Addison's disease (> 1000 pg/mL)
  • congenital adrenal hyperplasia
  • pituitary-dependent Cushing's disease
  • ectopic ACTH-producing tumors
  • Nelson's syndrome
  • hypoglycemia
• physiological increases seen with pregnancy, menstrual cycle & stress
  • nyctohemeral (sleep-wake) rhythm of secretion
    • highest levels 0600-0800 hours
    • lowest levels 2100-2200
    • oscillations may occur during the day
    • periodicity is abolished with hypercortisolism

* Functional tests may be useful for distinguishing causes of increased ACTH secretion:

• dexamethasone suppression test
  • Cushing's disease generally shows suppression
  • adrenal neoplasms & ectopic ACTH-producing neoplasms do not

Decreases

• pharmaceutical agents
  • dexamethasone & other glucocorticoids, heparinized plasma
• clinical disorders
  • secondary adrenocortical deficiency
  • adrenal adenoma or carcinoma
  • hypopituitarism

Methods

• RIA, IRMAm
• ACTH is unstable in blood
• most commercial RIAs measure ACTH precursors & fragments along with ACTH
• IRMA is specific for intact ACTH
• RIA is recommended for investigating ectopic tumors since many of these produce ACTH fragments

Specimen

• plasma (EDTA)
• place immediately on ice after collection
• freeze plasma within 15 minutes
• store frozen, preferable in plastic tubes at -70 degrees C
• aprotinin (Trasylol) 500 kU/mL added for long-term storage

More general terms

• corticotropin in body fluid

Additional terms

• adrenocorticotropic hormone; corticotropin; adrenocorticotropin (ACTH)
• dexamethasone suppression test

Component of

• anterior pituitary evaluation panel

Patient information

ACTH in plasma patient information