Corticotropin inhibitory peptide (CIP) is a 7-38 fragment of human ACTH (1-39), a peptide composed of 32 amino acids, and an antagonist of ACTH receptors. Experiments have shown that ACTH (7-38) does not have any corticosteroid activity. From the perspective of peptide synthesis, there are structural fragments such as Asn-Gly in the ACTH (7-38) sequence, which are prone to hydrolysis; secondly, there are more basic amino acids in the sequence and can be dissolved in acidic solutions.