This test measures the amount of 17-OHP in the blood. The 17-OHP test is used to screen for congenital adrenal hyperplasia (CAH) and may be used along with other tests to help diagnose and monitor CAH. 17-OHP is a hormone made by the adrenal glands, two glands located on top of the kidneys. The adrenal glands make several hormones, including cortisol. Cortisol is important for maintaining blood pressure, blood sugar, and some functions of the immune system. 17-OHP is made as part of the process of producing cortisol.