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ACTH (corticotropin) in plasma

Reference interval: 1) adults (0800 hours): < 120 pg/mL (26 pmol/L) 2) adults (1600-2000 hours): < 85 pg/mL (19 pmol/L) 3) newborn: 10-185 pg/mL (2.2-41 pmol/L) 4) cord blood: 50-570 pg/mL (11-125 pmol/L) 5) 9-52 pg/mL (2-11 pmol/L) [2] Increases: 1) pharmaceutical agents -> aminoglutethimide, amphetamines, insulin, L-dopa, metoclopramide, metyrapone, pyrogens, RU 486, vasopressin 2) clinical disorders: a) Addison's disease (> 1000 pg/mL) b) congenital adrenal hyperplasia c) pituitary-dependent Cushing's disease d) ectopic ACTH-producing tumors e) Nelson's syndrome f) hypoglycemia 3) physiological increases seen with pregnancy, menstrual cycle & stress -> nyctohemeral (sleep-wake) rhythm of secretion 1] highest levels 0600-0800 hours 2] lowest levels 2100-2200 3] oscillations may occur during the day 4] periodicity is abolished with hypercortisolism * Functional tests may be useful for distinguishing causes of increased ACTH secretion: -> dexamethasone suppression test a) Cushing's disease generally shows suppression b) adrenal neoplasms & ectopic ACTH-producing neoplasms do not Decreases: 1) pharmaceutical agents -> dexamethasone & other glucocorticoids, heparinized plasma 2) clinical disorders a) secondary adrenocortical deficiency b) adrenal adenoma or carcinoma c) 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: 1) plasma (EDTA) 2) place immediately on ice after collection 3) freeze plasma within 15 minutes 4) store frozen, preferable in plastic tubes at -70 degrees C 5) aprotinin (Trasylol) 500 kU/mL added for long-term storage

Related

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

General

corticotropin in body fluid

References

  1. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  2. Medical Knowledge Self Assessment Program (MKSAP) 11, 17. American College of Physicians, Philadelphia 1998, 2015
  3. Adrenocorticotropic Hormone Laboratory Test Directory ARUP: 70010

Component-of

anterior pituitary evaluation panel