This test is an alternative to 17-OHP (#5200) for improved  sensitivity and larger measurement range.

17-Hydroxyprogesterone is a C-21 steroid hormone produced in the synthesis of glucocorticoids and sex steroids. As a hormone, 17-OHP also interacts with the progesterone receptor. 

Measurements of 17-OHP levels are useful in the evaluation of patients with suspected congenital adrenal hyperplasia (CAH) as the typical enzymes that are defective, namely 21-hydroxylase and 11β-hydroxylase, lead to a build-up of 17-OHP.

In contrast, the rare patient with 17α-hydroxylase deficiency will have very low or undetectable levels of 17-OHP. 17-OHP levels can also be used to measure contribution of progestational activity of the corpus luteum during pregnancy as progesterone but not 17-OHP is also contributed by the placenta. 

The application of 17-OHP has been shown to be useful to delay premature labor in pregnancy.