Medical College of Wisconsin
CTSICores SearchResearch InformaticsREDCap

Short loop adrenocorticotropin (ACTH) feedback after ACTH-(1-24) injection in man is an artifact of the immunoradiometric assay. J Clin Endocrinol Metab 1989 Sep;69(3):678-80



Pubmed ID




Scopus ID

2-s2.0-0024468140   20 Citations


A recent report measured a decrease in plasma ACTH concentration by immunoradiometric assay (IRMA) during infusion of ACTH-(1-24) in humans. It was concluded that this decrease in ACTH concentration was due to short loop ACTH autoregulation. The present study demonstrates that the decrease in ACTH concentration measured by IRMA was due to an artifact of the IRMA. We injected 250 micrograms ACTH-(1-24), iv, into five normal male volunteers after overnight 2.5-g metyrapone administration. The ACTH concentration measured by IRMA decreased from 59.6 +/- 9.7 pmol/L before to 4.8 +/- 2.0 pmol/L 1 min after ACTH-(1-24) injection. The ACTH concentration measured by IRMA increased thereafter in a mirror image of the decline in ACTH-(1-24) measured by RIA. Addition of ACTH-(1-24) to plasma in vitro resulted in a decrease in the ACTH concentration measured by IRMA which was of similar magnitude to that observed in vivo. ACTH-(1-24) infusion in vivo or addition to ACTH-(1-39)-containing plasma in vitro decreased ACTH-(1-39) measured by IRMA by binding to N- but not C-terminal antibody without forming a detectable sandwich complex. We conclude that although ACTH short loop feedback may exist, it cannot be detected after ACTH-(1-24) injection with the use of a two-site IRMA.

Author List

Raff H, Findling JW, Wong J


James W. Findling MD Staff Physician in the Multi-Specialty department at Medical College of Wisconsin
Hershel Raff PhD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adrenocorticotropic Hormone
Reference Values
jenkins-FCD Prod-484 8aa07fc50b7f6d102f3dda2f4c7056ff84294d1d