At the 90-minute interval, assessing 17-hydroxyprogesterone (17-OHP) levels via dried blood spot (DBS) samples provides a crucial snapshot of the response to glucocorticoid therapy in patients with congenital adrenal hyperplasia (CAH). This timing allows clinicians to gauge the hormone’s concentration during a critical phase after administration, aiding in adjustments in treatment regimens to optimize outcomes and minimize adverse effects.