This test measures the amount of 17-hydroxyprogesterone (17-OHP) in the blood. 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.

A 17-OHP test helps diagnose a rare genetic disorder called congenital adrenal hyperplasia (CAH). In CAH, a genetic change, known as a mutation, prevents the adrenal gland from making enough cortisol. As the adrenal glands work harder to make more cortisol, they produce extra 17-OHP, along with certain male sex hormones.