The ACTH 120-min test is performed by administering synthetic ACTH and measuring adrenocorticotrophic hormone levels after 2 hours. The test helps healthcare providers evaluate baseline adrenal gland function and adrenal response to synthetic ACTH stimulation.  The test provides insights into the hypothalamic-pituitary-adrenal axis. A suboptimal increase in cortisol level indicates adrenal dysfunction, guiding treatment decisions. ACTH serial increment is assessed; >50% increment is considered positive.